Friday, August 31, 2007

But he has nothing on!

Hans Christian Andersen
Denmark has a good reputation as an export nation of fairy tales. As soon as I have been able to read books, I have liked Hans Christian Andersen and in particular his Emperor's New Clothes. And I never have dreamt of once being in the role of the little girl that said: But he has nothing on! But today is the day.

The story begins in the Ugeskrift for laeger, a Danish medical journal of a good reputation. This journal has published a study in Danish language, where an abstract in English is available at PubMed: The cost of obesity on the Danish health care system.

The study authors have analyzed medical and economic data and have fabricated a piece of cloth and present it to the public. But when I take a closer look at it, I see that it is made out of nothing. The weavers have woven air, just as in the fairy tale.

The study in brief: Based on earlier studies that figure out the number of obese Danes, and on other studies that figure out the risk of various diseases in the obese, the authors have estimated that 177 thousand obese persons that have been treated in hospitals in 2003, causing estimated costs of 137 million Euro. In the conclusion, the authors say that these health-economic costs are related to obesity.

Nothing but air

What does obesity-related mean? Nothing more than this: A patient is sick, lying in a hospital bed, and doctors say that he is obese. We call this a correlation. Or a relation if you want. Anyway, this proves nothing. In particular, it does not prove any cause. If studies fail to prove that obesity causes disease, this "relation" would be meaningless, nothing but air.

In fact, this is what studies tell us: Obesity is NOT established as a major cause of disease, possibly as a weak cause in some diseases. And this effect is offset by a possibly greater positive effect because, among the sick, the obese have better survival odds than the so-called normal-weights. (Cynical remark: patients who die fast are less of an economic burden.)

Junk health economics

This is not yet the end of the story. The Emperor's New Clothes aren't worth anything if they are not presented in public. Such a presentation is what the title does: "The cost of obesity on the Danish health care system." I turn it back and forth in my head, and always find that they mean a cause and not a simple (meaningless) correlation. They call obesity even more than a cause of disease, but itself a disease, its spread being an "obesity epidemic". Obviously, I am too stupid to see this cloth.

Dear reader, please help me. Can you see any cloth here? Any tissue woven from hard, proven facts? If so, drop me a mail - your find it in the top link of my sidebar. If not, you may help me spread the real truth to the world: He has nothing on!

Photo source: Wikipedia

Thursday, August 30, 2007

Interview with Linda Bacon on weight and health

Linda Bacon
Linda Bacon is a strong advocate of the Health at Every Size movement and pleads for ending the war on obesity (don't miss her video message over there). She earned her doctorate in physiology from the University of California, Davis, specializing in weight regulation. She also holds graduate degrees in both psychology (specializing in eating disorders and body image) and exercise science (specializing in metabolism), and has professional experience as a researcher, clinical psychotherapist, exercise physiologist, and educator. In addition to serving as an Assistant Researcher in the Nutrition Department, Dr. Bacon teaches Nutrition in the Biology Department at City College of San Francisco and conducts trainings for health professionals on the latest research in weight regulation.

She has agreed to answer the tough questions of Med Journal Watch. And here we go!

Christian Bachmann: Prior to this interview you have been so kind to let me calculate your body mass index. You have the same as mine, 21. Isn't it easy to tell people that being fat is no problem when it is not your problem?

Linda Bacon: When I say that fat is not a problem, don't get me wrong - I believe that FAT STIGMA is a huge problem - for all of us. I do understand that it is extraordinarily difficult to live in the world in a stigmatized body. I'm suggesting that we fight the stigma as opposed to trying to make fat people change (get thin). When we observe racism, it just isn't valuable to encourage people of color to lighten their skin - or to tell them they're somehow wrong. The stigmatization is also wounding for people who are not fat as they have to live in fear of becoming fat.

CB: I agree. But if you were fat, I could argue that your statements were just sort of an excuse for being fat.

LB: I have frequently noticed my "thin privilege" in the world - that people often take what I say more seriously than when a fat person says the same thing. A lot of fat people have figured out the same things that I have. And their voices can be powerful also, perhaps even more so as they can be role models of living proud, happy lives in a body that's culturally feared and held up as wrong - that takes an incredible strength and self-confidence.

CB: You disagree with the majority of weight experts. They tell us that overweight is one of the leading causes of premature death, for instance from heart attacks, but also from diabetes and other diseases. Why do you disagree?

LB: I disagree because I have looked at the evidence. Reputable studies, published in well-respected, peer-reviewed journals, actually show that people in the "overweight" category live longer than those in the "normal" weight category.

CB: And what makes you sure that you are right and they are wrong?

LB: My experience from having worked closely with many obesity researchers who are more conventionally-minded than me is that they are so strongly mired in their assumptions, that they don't look at the evidence. Those that willingly engage, change their beliefs. The evidence is quite convincing.

CB: You said that weight increase and diabetes share common causes, in other words, that weight increase is a parallel outcome together with diabetes and not a cause of diabetes. Normally, high quality studies are controlled for such common causes. For instance, the effect of a sedentary lifestyle could be filtered out in a multiple regression statistics. Hasn't obesity been established as an independent cause of illness and premature death?

LB: Yes, weight sometimes plays a role in increased disease risk. I don't dismiss that entirely - rather what I am saying is that role is greatly blown out of proportion. While it is possible - and should be required - to control for a sedentary lifestyle and other counfounders, many studies don't. In the case of type 2 diabetes, studies show improvement can occur through lifestyle change, even in the absence of weight loss. It's much more productive to address the diabetes through lifestyle change. This is even more important when you consider that we don't have a proven way to accomplish weight loss - and how damaging the quest for weight loss can be.

CB: Let's come to another important point. What is right for some may be wrong for others. There are some studies on the "obesity paradox", as they call it. In patients suffering from various diseases, the obese have better survival chances. The same is true for persons older than sixty years. But what about children? Is it really okay for them to have a body mass index of thirty or more?

LB: All kids can benefit from good lifestyle habits - why do we have to pick on the fat kids?

CB: If people are fat and sick and if they lose weight and get cured, this could be a proof that fatness causes disease. Has there been any such outcome in a study?

LB: That seems like an impossible study to conduct. You would have to control to make sure that nothing changed other than their weight. They would have to be doing something differently to lose weight. For example, suppose they exercised more - you couldn't attribute the health improvement to the weight loss as it might have come from the activity changes.

I suppose you could look to the surgical studies to see the effects of weight loss without changing lifestyle factors. Gastric bypass surgery appears to reverse diabetes within days, before significant weight is lost, suggesting that it is not the weight loss that brings about the improvement, but probably some other factor (such as a change in the release of gut hormones).

There was also a liposuction study that examined weight loss in diabetic women. Despite the weight loss, their metabolic profile did not improve, including their fasting glucose and insulin levels or their insulin sensitivity.

CB: How much do they lose anyway, in the long run? What is the average weight loss five or ten years after the beginning of the fight against fat?

LB: All the long-term research shows that the majority of participants on diet and exercise programs regain ALL of the weight. There has been remarkably little long-term research on surgical outcomes, but even that is showing long-term weight regain, albeit much further down the line. And that's in addition to introducing a lot of "complications."

CB: I have the impression that body weight trends go to the extremes. Some gain more and more weight, others get thinner and thinner. Am I right? And where do you see the causes?

LB: Among thinner people, nothing has changed, not even by a few pounds. Move up the weight scale, and people are putting on a few pounds. Get to mid-range and people are just 6 or 7 pounds heavier than they were in 1991. It is only with the very heavy, at the extreme of weight, that there is a substantial increase in weight, about 25-30 pounds.

No doubt our lifestyle habits have changed during this time frame. Genetic differences result in people having varying degrees of susceptibility to weight gain - even under the same environmental conditions (meaning eating, activity and other habits).

CB: Any treatment should follow the rule "first do not harm". Does the war on obesity meet this rule?

LB: Sounds good to me. Seems clear its time to end the war, which we're clearly losing anyway. There's a antidote to the war on obesity, called "Health at Every Size" which supports people in engaging in healthy lifestyle habits as opposed to a primary focus in weight loss. I envision it as a peace movement.

I conduct research on Health at Every Size (HAES). The results show that women can make very dramatic improvements in health and well-being through adopting HAES. These results were particularly dramatic when the women in the Health at Every Size program were compared to others in a conventional weight loss program. Those in the weight loss program experienced the typical results - initial weight loss and health improvement - not sustained over time. And their self-esteem plummeted. This was in sharp contrast to the phenomenal improvements experienced by the women in the Health at Every Size program, who felt very much empowered.

CB: Thank you, Linda, for giving us a fresh view on a problem that only seems to be a problem because we make it a problem. I hope you'll help a lot of people to enjoy what they eat and to live healthy at every size.

LB: Thanks for the interest, Christian. It's important to be discussing these issues. It's been hard to give short responses to your questions. I have examined them all in a lot of depth. In fact, I'm just finishing a book on this topic. Health at Every Size: Finding Your Happy Weight, will be coming out in June 2008.

Linda Bacon's homepage
Health at Every Size

Photo credit: UC Davis

Wednesday, August 29, 2007

Stress is in the hair

Good doctors listen to their patients and find out how they feel - see also the excellent Grand Rounds on Narrative Medicine. One very important condition is stress because it can turn many diseases to the worse. - Stress can also be measured in the lab. A new study has found a strong relationship between stress and hair cortisol in healthy pregnant women. Cortisol is a stress hormone circulating in the blood but also reaching the hair roots where it deposits. Thus, a researcher does not have to ask if you have been stressed in the past weeks or months, he just tears out some of your hair, puts it into a test tube and gets your stress value.

Basically, this is a good thing. Research will get more precise results when surveys about self-perceived stress are backed up with hard facts. Thus, in the long run, we may get better insight into the connections between stress and various diseases. The study authors conclude:

"This new long term biological marker may have important implications in research and clinical practice."
Clinical practice? As a patient, I'd rather prefer my doctor talking to me about how I feel, stress included, than watching him quietly tear out my hair.

Photo credit:

Health Blog Carnival Watch 1:9

Grand Rounds 3:49
This week's theme is Narrative Medicine. Susan Palwick presents her selection of the thirty best medical posts of the week and, even more, tells us about how Narrative Medicine, by training doctors and nurses in careful listening and reflective writing, can lead to a better care. It is interesting to see how the posts fit into this concept. Medical blogging, it seems, is a special form of Narrative Medicine. Enjoy!
August 28, 2007 at Rickety Contrivances of Doing Good

Gene Genie #14
This edition is about bugs and beyond. Ajcann presents a number of hot genetic topics such as genetic counseling, new discoveries about genetic diseases, genetic legislation and much more.
August 26, 2007 at MicrobiologyBytes

Tuesday, August 28, 2007

Face surgery beyond lifting

face lifted
For all those who suffer from severe facial injuries or birth defects, the news from the surgical reconstruction front sounds good: There is a number of methods for filling up lost volume and reconstructing a face that proudly can be shown in public again.

Just to mention some: Autologous fat (fat cells harvested from other parts of the body), calcium hydroxylapatite, poly-l-lactic acid, polyacrylamide, poly-alkyl-imide, and methylpolysiloxane. I do not go further into details, just - wow - it seems that facial surgeons have a number of good stuff to do a good job.

However, the study from where I got this news is not about reconstruction but about the third dimension in facial rejuvenation. A quote from the abstract:

"Facial rejuvenation has long been dominated by surgical techniques that act on only two dimensions of the face, ignoring the third dimension (facial volume); therefore, a truly youthful look remains elusive. (...) This paper aims to define the various surgical procedures employed by cosmetic surgeons that can be combined with alloplastic implants or injectable devices in order to restore lost facial volume."
I understand well what this means. We all know those face-lifted old ladies, many of them in the show business, with their smoothed faces that do not really look young but old and rejuvenated. It seems that modern face surgery is going to address this problem. In the future, lifted old faces no longer should look lifted, they should look really young.

But I already see a new problem: Young faces on old bodies cannot look really young but look strange, to put it mildly. Therefore, whole body rejuvenation must be the inevitable solution. Let me extend this story into the realms of science-fiction and we end up with old, young-looking cyborgs, a lost generation of no-agers whose rest of own body mass will suffer from a number of diseases. Not only from the old ones as we know them, but in addition from all those that are caused by the side effects of surgery.

Related post: Double suicide rate with breast cosmetic

Photo credit:

Monday, August 27, 2007

How kids live better with their asthma

Parents should encourage their asthmatic children to be active, to take part in sports and play with others and teach them what to do in case of an attack. With such an active coping, the children's quality of life is considerably better than if parents try to avoid everything that might provoke an asthma attack. This is the result of a survey in more than eighty mothers and their asthmatic children.

Childhood asthma has a good prognosis. About half of the children outgrow the disease. It is important to make sure that the disease, as long as it may last, does not take control of life.

Photo credit:

Saturday, August 25, 2007

The art of lying with statistics

Are you afraid of this monster? I would guess no, because this is just a small water flea called daphnia. But when I was a student of preclinical medicine, sitting in a biology course and looking through a microscope, I shrug back with shock when a daphnia all of a sudden jumped into my magnified field of vision. Mountain or molehill - it is all a question of perspective.

This also holds true for an article that I just have read in my newspaper: "Overweight surgery reduces mortality." The article reports a 30 percent reduction of mortality risk after bariatric surgery in Sweden.

Thirty percent, this sounds impressive if we are not aware that this figure comes out of a statistical microscope. It seems to prove that overweight is a cause of death and that the risk can be reduced by a considerable amount if we lose weight.

But let's have a look at the facts and figures. In Sweden, 2010 people with an average body mass index of 42 have been treated by gastric surgery and have lost between 14 and 25 percent of body weight during ten years after surgery. Another 2037 people with the same BMI average have been treated conventionally, and their weight remained stable in a range of plus/minus 2 percent of body weight. After ten years, 101 persons of the surgery group and 129 of the control group have died.

How to make 30 percent out of 1.3 percent

Now we begin to see how the statistical microscope works. It ignores the vast majority of persons who survived and puts the focus on the 6.3 percent mortality in the weight-stable group and 5.0 percent mortality in the weight-loss group. That is, the risk has been reduced by 1.3 percent. This is not much, you may even call it meek. But you can calculate a relative risk: Blow up the 6.3 percent to a full hundred percent, then 5 percent equals 79 percent, and you got a relative risk reduction of 21 percent. You may do even more and blow up the 5 percent to a full hundred percent, and you get even higher figures. Then you can control for sex, age and risk factors and get an adjusted hazard ratio of 71 percent, that is, a relative hazard reduction of 29 percent. Round it up and you get the 30 percent reported by the newspaper.

The misleading term "overweight"

The Swedish study has been done with extremely obese people. I am ready to accept that extremes cannot be very healthy, be it a fashion model with a BMI of 16 or a man with the stature of a sumo wrestler and BMI 50. Therefore I am not very surprised to see a small positive effect on health with a massive change of metabolism (weight loss is not necessarily the important point) in very obese persons. But this has nothing to do with "overweight" as stated in the newspaper headline.

"Overweight" is widely used for persons with a body mass index higher than 25. The story reported by the newspaper has nothing to do with this group of people. But the headline will once again make them believe that they should lose weight in order to get healthier. A view absolutely not supported by the report.

Photo credit:

Friday, August 24, 2007

Can fat be fit? A review

scientific american
In the September edition of Scientific American, Paul Raeburn, a senior science writer, makes himself an advocate of the war on obesity. In his opinion, there is no reason for a peace, and the war should go on.

He attacks a study by Katherine M. Flegal of the Centers for Disease Control and Prevention, who has found that mildly overweight adults have a lower risk of dying than those at so-called healthy weights. He does not directly criticize this study but just cites an expert who says that Flegal is wrong. Her analysis is said to be flawed because she did not exclude the smokers and seriously ill people: "When you get sick, you lose weight and you die". Thus, the overweight are not better but the slim on average are worse.

Then he admits that Flegal has just recently published a follow-up of her study where she has accounted for the impact of smoking and serious illness and found that this did not change the results. At this point, Raeburn has no other than claiming a majority of experts supporting his view whereas the weight loss skeptics are only a handful. Not very convincing given the heavy investments of the weight loss industry being at stake!

Thursday, August 23, 2007

Facts on body fat and heart attacks

happy couple
For an average person of average age with a body mass index (BMI) between 19 and 25, the risk of suffering from coronary heart disease is about 9 percent. Under the same average conditions, but with a body mass index of 30 and more, the risk of heart disease is increased by a relative amount somewhere between ten and a hundred percent - with a likeliness of 95 percent. This increase will push the absolute risk from 9 to 10 percent in the best case or from 9 to 18 percent in the worst case. (Source: A consensus paper of the Swiss Expert Group on Obesity and Metabolism, 2006)

These figures are just correlations and tell us absolutely nothing about a possible cause. Thus, if a so-called obese person manages to lose weight, it is quite unlikely that this will reduce the risk of a heart disease. As far as I know, all these experts advising people they should lose weight have no hard facts to prove that this really reduces the risk of a heart attack or other diseases.

A thought experiment on weight loss

Just let me do a little thought experiment here. I'll try to assume conditions that are in favour of weight loss adepts. I do not share them. I just assume that half of the risk increase should be directly attributable to body fat and that it is completely reversible by weight loss. I also assume that there is such a thing as an average person and that general recommendations can be drawn from the statistics.

First step: The relative risk increase that may be prevented by weight loss is between 5 and 50 percent which translates to an absolute risk increase between 0.5 and 4.5 percent - but only if our average person manages to reduce his or her body mass index by ten points, let's say from 35 down to 25.

Second step: Most weight loss trials show BMI reductions of about 2 points, but let's be generous and assume a loss of 5 BMI points. This is half of the required amount for the above risk increase prevention. Let's assume further that half of the reduction will bring half of the preventive effect, that is, between 0.25 and 2.25 of the absolute risk that could be prevented by the weight loss.

Conclusion: Given the fact that I have set the conditions in favour of the weight loss adepts, this outcome of my thought experiment is quite pathetic.

Photo credit:

Wednesday, August 22, 2007

Obesity paradox: More risk, better outcome?

myocardial infarct
A heart infarct (dark spotted area in this microscopic image) is likely to be smaller in obese than in normal-weight patients. This outcome of an Italian study adds further evidence to the so-called obesity paradox.

The term obesity paradox describes a puzzling conflict of observations on body weight and the risk of death from a heart attack: When we look at the population as a whole, obese persons have a higher risk of dying from a heart attack. But when we look at patients suffering from a heart disease or having survived a heart attack, the obese are less likely to die than the normal-weight. In short, the obese have a higher risk but a better outcome.

For this paradox I see three possible explanations that are not mutually exclusive:

  • Scenario 1: Bad and good body fat. A higher mass of body fat is the cause of sickness in general and heart disease in particular. Once the heart is attacked, body fat has a protective effect. But this effect does not outweigh the negative impact of body fat: Obese persons are still more likely than normal-weight to die from a heart attack. The protective effect of body fat only can be seen in normal- or underweight heart patients who have a worse outcome than the obese.
  • Scenario 2: Bad metabolism and good body fat. A higher mass of body fat is caused by a bad metabolism (unhealthy nutrition, lack of physical activity, genetic influences) that is also the cause of sickness in general and heart disease in particular. Body fat as such has no negative influence but a protective effect once the disease has developed.
  • Scenario 3: Bad metabolism and self-repair. There is no causal relationship of body fat, neither with the risk of disease nor with the outcome. The accumulation of body fat and the development of a heart disease have the same underlying causes in the metabolism. Later, when the disease has developed, the body fights it with self-repair mechanisms. Again, body fat is not a cause of such mechanisms but only a concomitant outcome.
At the moment, scenario 2 makes most sense to me. Firstly, there is little evidence that body fat as such causes heart disease. And secondly we should remember why the human body accumulates fat: As a reserve for bad times when energy input is low and energy demand is high. A sickness, certainly, is a condition of higher demand. Thus, it makes sense to me that a reserve of fat helps the body to cope with disease.

Photo credit: Wellcome Photo Library

Health Blog Carnival Watch 1:8

After having done some hosting recently, I have to catch up with a number of great carnivals that have been published meanwhile.

Grand Rounds
3:48 Back to School - an excellent collection of posts with an educational approach. August 21, 2007 at Med-Source
3:47 Sudden Changes - August 14, 2007 here at Med Journal Watch
3:46 Beach House Edition - a nicely presented edition inviting you to relax, take your time and enjoy. August 7, 2007 at Eye on DNA

Medicine 2.0
A great resource guide for users of medical blogs and for medical bloggers.
August 19, 2007 at Sharp Brains

Skeptics Circle #67
Bronze Dog presents a mighty arsenal of giant robots and secret weapons to fight fallacies and pseudo-science.
August 16, 2007 at Bronze Blog

Tangled Bank #86
Sarda Sahney presents a broad collection of best posts on various fields. The section of human biology, diet and medicine reports about vegetarianism, pre- and probiotics, hormone and diabetes, brain improvement research and the unconscious signals between the sexes.
August 14, 2007 at Fish Feet

Gene Genie #13
Blaine Bettinger presents new aspects in the exciting field of genetics, personal genetics and personalized medicine.
August 12, 2007 at The Genetic Genealogist

Carnival of Nourishment #5
Joanne Hay presents posts about milk, probiotics, the glycemic index, green beans and quality food. Enjoy your meal!
August 4, 2007 at Nourished Magazine

Tuesday, August 21, 2007

Breastfeeding gives parents more sleep

baby sleeping
New parents sleep forty minutes longer, on average, if their baby is breastfed all the time, compared to additional formula feeding in the evening or at night. This is the result of a study with more than a hundred new parents and their first babies in California.

The main reason for giving formula supplement in the evening or at night is the hope that baby may be more quiet and let parents sleep better. Obviously wrong!

This study did not examine the difference between exclusively breastfed and exclusively formula fed babies. Thus it remains unclear what makes babies sleep worse: Is it the formula or is it mixing human milk and formula milk? Whatever, the authors conclude:

«Parents who supplement their infant feeding with formula under the impression that they will get more sleep should be encouraged to continue breast-feeding because sleep loss of more than 30 minutes each night can begin to affect daytime functioning, particularly in those parents who return to work.»
But what about mothers who haven't got enough milk? Read the advice I got from the Australian Breastfeeding Association in response to my post in the comment below.

Photo credit:

Comment from the Australian Breastfeeding Association
This is a subject close to my heart as I am manager of the Australian Breastfeeding Association Lactation Resource Centre. I would just like to comment that there are of course rare maternal conditions that will affect the ability to produce a full supply but the major causes of low supply in the developed world are; not feeding the baby often enough; a lack of knowledge about how the milk supply works; a lack of knowledge about normal baby feeding and sleeping behaviour. Briefly milk is produced in response to demand. The baby feeds and the milk producing cells in the breast are stimulated to produce milk. If a baby is not feeding well a mother may have to express her milk to keep up a good milk supply. Normally a mother needs to do nothing more than offer the breast when the baby shows signs of hunger. This will ensure demand and supply will be in sync. If you are interested in this topic on a more scientific level please look up the publications from the research team of Professor Peter Hartmann. Also the International Society for Research Into Human Milk and Lactation website.

Kate Mortensen IBCLC, Australian Breastfeeding Association Counsellor

Monday, August 20, 2007

Women a key to better health

isle of women
Iran is planning a bizarre holiday resort: An island for women only. As the strict codes of Iran prohibit exposure of unveiled women, the planned resort is expected to become very attractive, a paradise for female tourists. Men will not be allowed on the island.

Sexual apartheid is one of the main reasons for the big gap between poor and rich countries in the world, according to David S. Landes, Harvard professor of economics and author of The Wealth and Poverty of Nations. In an interview to Challenge magazine, back in 1998, he has put it as follows:

«The Middle East, particularly the Muslim Middle East, is in great trouble. Cultural attitudes there are a barrier to development. I stress relations between men and women and the sexual discrimination that results; obviously, this is not saying anything new. When you treat women as a source of danger or pollution to be cut off from the public space and limited in permissible economic activities, you lose a large portion of the potential productivity of the society. But where I say something new is that I stress the implications of these relations for the men. A system that privileges the men from birth on, simply because they are male and that gives them power over their sisters and the other female members of society, is bad for the men. It builds in them a sense of entitlement that discourages what it takes to improve, to advance, and to achieve. One has to understand that this is not something limited to the Arab Middle East, or to the Muslim Middle East. It is found in different degrees all around the world, and even those of us who live in so-called advanced industrial societies are guilty of the same thing. And we are still struggling against it and trying to define the meaning.» (Source:
Why is this a health issue? Because economy is a major health factor and the worldwide map of health disparities fits pretty well the map of economic disparities.

And why is this an issue for us who live in so-called advanced industrial societies? Because we, in our attitude to women, may be somewhat better than the ayatollahs (or the Vatican), but still far from a society with equal rights and values of women and men.

Photo credit:

Saturday, August 18, 2007

Important step 45 years after Silent Spring

nile tilapia
Rachel Carson, one of the greatest environmentalists of all times, would have loved what I report here: In search of a better way to fight malaria, scientists in a region of Kenya have turned away from DDT and used a fish called tilapia instead. Tilapia feeds on mosquito larvae. As a test, tilapias have been introduced in one pond, and a second pond has been left without fish as a control. During half a year, both ponds have been observed. The results are encouraging: The tilapias have eliminated 94 percent of the malaria mosquitoes in the test pond.

And even better: Tilapia is edible, already a popular food in Kenya, and offers an important source of protein for the people and a source of income from fish farming.

Resistance: An old problem must be solved today

Rachel CarsonRachel Carson, with her landmark book Silent Spring, has initiated a shift in awareness that, within ten years, led to a ban of DDT in the United States. But she never has claimed a ban of DDT against malaria. She only warned against the drawbacks of resistant insects and suggested a well-dosed approach:

«No responsible person contends that insect-borne disease should be ignored. The question that has now urgently presented itself is whether it is either wise or responsible to attack the problem by methods that are rapidly making it worse. (...) Malaria programmes are threatened by resistance among mosquitoes. (...) Practical advice should be 'Spray as little as you possibly can' rather than 'Spray to the limit of your capacity' (...) Pressure on the pest population should always be as slight as possible.» (Source: Wikipedia)
As predicted by Rachel Carson, resistance in malaria mosquitoes against DDT and other pesticides has grown so strong today that only biological control methods can offer sustainable solutions. If the Kenyan tilapia research will be put into practice in rural Africa, this could be one of the rare good news from this continent.

Photo credits: Niall Crotty and U.S. Government

Friday, August 17, 2007

Medical study concluding for dummies

If you read the abstract of a medical study, you'll be confronted with the conclusion of the authors in most cases. My advice: Do not buy it but draw a conclusion of your own. Here is an example where this task looks not too difficult.

The numbers in the table below are odds ratios for preterm birth, drawn from half a million birth records of Missouri. Births from white mothers and white fathers serve as a reference.

white father black father
white mother1.001.13
black mother 2.102.28

What do you conclude from this table?

I guess that you see a big difference between the upper and the lower row and a much smaller difference between the left and the right column. This is not difficult to explain. Obviously, for black mothers, the odds of a preterm birth are double as high as for white mothers. There is also an effect for black vs. white fathers, but it is by an order of magnitude smaller.

So far so simple. Now, what to you think about the causes of this disparity? The following possible reasons may come to your mind, conditions that could be different in black and in white women:
  • health status
  • income
  • education
  • maternal age
  • stress
  • social support
  • lifestyle
  • etc.
What do the study authors conclude from this table?

The study has been published under this title: Paternal race is a risk factor for preterm birth. You may think this is a typo given the fact that the influence of maternal race is nearly ten times as big. But it is no typo. The authors conclude:
«Paternal black race is associated with an increased risk of preterm birth in white mothers, which suggests a paternal contribution to fetal genotype that ultimately influences the risk for preterm delivery.»
Racists would very likely draw such a conclusion, but maybe the authors know more than we do. They may see the big difference in black and white mothers as a given fact that is widely known and covered by research. They may point out one additional finding, not a big one but a new one. But their conclusion is most likely to be used by racists.

Why the %*¿k do the authors leave aside the main finding and comment on the tiny fraction of a tiny fraction? If you translate the odds ratio to a relative risk and then to an absolute risk difference, this will be close to zero.

I am not a specialist in genetics, gynecology and obstetrics but I have my strong doubts if the genetic explanation of the authors is the most plausible one. I suspect that this is a case of undue jumping from correlation to cause. Nowhere in the abstract I can find any mention of controlling for factors or that the odds ratios are adjusted.

We need more evidence

In search of more facts that may solve this case I have found a study on the black/white difference in neonatal mortality, mostly from preterm births and low birthweight and in the same magnitude as found in our table. Can you believe that mortality at birth may have a genetic cause? I can't.

Photo credit:

Comment by James A. Grant
The big difference in preterm births between black and white mothers is widely known and covered by research. This is not a novel conclusion and likely why the authors did not make comment of it. In addition, there is evidence that correcting for socioeconomic status does not fully account for this difference, leading to an alternative hypothesis: there may be genetic bases for the observed difference.

Why should there be a paternal role in the likelihood of preterm birth particularly since it is only necessary that a male contribute his gametes at conception? Does a genetic explanation here truly seem so outlandish, particularly given others’ work on differing genetic polymorphisms among racial groups.

What do the authors’ conclusions have to do with racism and on what basis do you justify associating (if not accusing) the authors with racism? Empirically, the conclusion the authors reached is reasonable: Paternal black race is associated with an increased risk of preterm birth in white mothers. Causality remains undetermined BUT, given a wider body of research examining racial variations in genetic polymorphisms and the role on preterm births, paternal genetics remains a legitimate hypothesis for the reported study observations.

You can’t believe that mortality at birth may have a genetic cause? I guess you might also not believe that disorders such as Turner’s and Down Syndrome don’t have a genetic cause.
Author's reply
The control for socioeconomic status is fine and obviously explains a part of the difference. But the rest is not necessarily genetic factors; there may be other factors that should be controlled before we can make such a statement.

As you clearly state I do not accuse the study authors of racism. My association comes from the fact that I have read many racist statements based upon scientific findings, and this one may be very ready to be misquoted in such a way.

As to a possible genetic cause of mortality at birth: You are right. I have to correct myself and should put it this way: Can you believe that mortality at birth may have a genetic cause other than a genetic disease? While Turner and Down syndromes are such diseases, a black skin certainly is not.
Final comment
Thanks for your reply, Christian. I enjoy your blog and I agree with your assessment that scientific findings are consistently mischaracterized in the media and, particularly in ethnicity related research, have the potential for gross misuse. So I think you are performing a valuable service in providing a better context for understanding of literature. Keep up the good work.

James A. Grant, Duke University

Thursday, August 16, 2007

Too weak evidence against body fat

fat and smoking
While I have been scanning new PubMed entries recently, this study jumped into my eyes: Smoking status and adiponectin in healthy Japanese men and women. It was adipo that made me click into the abstract of this study. The prefix adipo means fat-related, and as you may know from my earlier posts I am looking for any possible evidence of a direct and negative body fat effect on health.

Adiponectin is a hormone produced by human fat cells. It is thought to have various positive effects on health, reducing the risk of atherosclerosis, coronary heart disease and type 2 diabetes. The Japanese study shows that smoking reduces the level of this healthy hormone. In those who have quit smoking for more than twenty years, the hormone levels are the same as in non-smokers. Thus, smoking is likely to be the cause of the lower hormone level. A lower adiponectin level may be one negative effect of smoking on health, but surely it is not the only one.

Despite being produced by fat cells, adiponectin is lower in people with a higher fat mass. The more body fat, the less of the good hormone adiponectin. So it seems we have found a direct negative health effect of body fat.

Weak multiplied by weak equals (nearly) zero

The adiponectin case is too complicated to be discussed in full details. So I must make some simplifications here. Let me assume that a higher body fat mass is the ultimate cause of a lower adiponectin level and that this lower level is the cause of a higher heart disease risk. This is not necessarily so, but just assumed, it would be in favour of the bad body fat theory. But even this is not sufficient, as we just will see.

adiponectin graphBody fat, adiponectin and heart disease are not pieces of a domino where one falling piece is sufficient to make the next piece fall. In contrary, the effects are only weak. In obese people, the adiponectin levels are not zero but only about twenty or thirty percent lower than in slim people (see graph).

And in people with atherosclerosis (a risk factor for heart disease), this difference against healthy people may even be smaller, for instance it has been found not statistically significant in a Polish adiponectin heart risk study.

Take home message: A higher mass of body fat may lower the level of a healthy hormone to a small amount and this healthy hormone may have a very small influence on the risk of a heart attack. The cascade of these two weak effects is most likely to be smaller than detectable.

Photo credit:
Graph credit: Obesity Research

Tuesday, August 14, 2007

Grand Rounds 3:47

sudden change

Featuring Sudden Changes Of All Kinds

Grüezi* and welcome to Grand Rounds! (*hello in Schwyzerdütsch) The hosting plan of this edition has gone through several sudden changes. First I wanted the date of our National Day because, to my knowledge, this is the first time that Grand Rounds are being hosted in Switzerland. But the date already had been taken, so I planned to hack the World Economic Forum website. Their focus is too much on money in my opinion, and replacing their content with Grand Rounds posts could have opened their eyes to what really counts in life. All had been ready so far, pixel number thirty-seven in the WEF logo already been changed testwise. But then it struck me like a flash of lightning: What really counts is content and not the outer form.

It was the day after my sudden change of view on weight loss (see sidebar), and I said to myself: One giant leap for my blog, but only one small step for the medical blogosphere. There must be sudden changes of other dimensions, of real importance out there. And here they are.

I begin with a post specially written for this edition. Val Jones tells us the tragic story that brought her to raise her Voice of Reason at Revolution Health: «My road to a revolution.» Blogging and online information as a weapon to fight the shortcomings of a corrupt health system. Very encouraging for us fellow health bloggers!

Jenni Prokopy's way to Chronicbabe has been very different but not less dramatic. In a sudden shift of view she has come to accept her chronic illness which gave her the power of turning her former hobby blog into a full-time career. Very impressive!

Challenged by the theme of this edition, Kim at Emergiblog suddenly
sees sudden changes everywhere in her life, in private as well as in emergency department nursing. Don't miss the wonderful scene with the four years old skeptic!

And now I have the pleasure to introduce Dr. Bee in our midst. She just has started her new blog Postcards from Kiddieland, telling us how she reacted instinctively on a sudden change to the worse.

Changes of view

It was Sunday morning, I was reading my newspaper and found the story of Oscar the cat that predicts death. The article reported this as a fact without any doubt. Normally I would have bought it, we all love interesting stories and I am a journalist myself. But Sandy Szwarc of Junkfood Science is a must-read in such situations. It is important not to be fooled. Nor by allegedly prophetic cats nor by quacks. Sandy, to my surprise, tells us that even scientists can be fooled - by jumping from correlation to cause and by the confirmation bias. By the way, here is the initial trigger that brought me to our Grand Rounds theme.

#1 Dinosaur, in his musings blog, tells us a story that somehow reminds me of Chronicbabe. Parents have to deal with the inevitable fate that their baby cannot be cured. It suffers from sort of a Phantom of the Opera mask: A picture is worth a thousand words.

Rima Bishara, the Doctor Blogger, tells us about the dramatic changes in view that take place in parents raising a disabled child.

David E. Williams of Health Business Blog always has been against limited health insurance plans (Mini-Meds). But then he came to think it over and found a new, positive understanding that also made him start a medical tourism project.

The war on obesity leads to strange changes: Tony Chen reports a case of a hospital that cuts paychecks for workers with a body mass index of more than 30. Studies show that obese hospital patients survive better. And hospital managers punish obese workers? We live in a strange world, indeed.

Another serious issue: Cancer fears that put people under stress despite lacking evidence. Gloria D. Gamat of Daily Diabetic describes how she has changed her mind by interviewing an expert: Sugar substitute and cancer - there is really nothing to fear!

How To Cope With Pain reports a finding that migraines may be caused by a hole in the heart. Very surprising. Time will tell if this will lead to a shift of view in the understanding of this pain disease.

Changes to the worse

The next post is dedicated to Ylenia, a five years old Swiss girl who recently disappeared. Other than in the Maddy case, more and, I hate to say, worse things are known to the police. All (!) of her clothes have been found. The suspected rapist happens to be a former resident of a village only three miles from where I live. He has killed himself with a gun. Ylenia has not yet been found. Whole Switzerland is shocked. I cannot bring Ylenia out of my mind when I read what Vitum Medicinus in his blog tells us: The sad story of a boy whose life has been destroyed by a rape. - Update: Ylenia has been found dead, poisoned by toluene and without detectable traces of rape, and traces of clandestine pedophiliac activities of the killer have been found.

Another dramatic story is told by Terry Freemark a nurse anesthetist blogging at Counting Sheep: A patient who dies on the operating room table from multiple gunshot wounds.

Laurie Edwards, in A Chronic Dose, recently had to tackle the sudden death of a near person and tells us how she found a positive spin, based on her experience with chronic illness: Mourning thoughts.

Adam, at NY Emergency Medicine, describes how it feels negotiating death with a terminally ill patient who cannot make up his mind whether to be intubated or not. A strong piece!

Even if intubation seems all to be normal, things can suddenly turn to the worse. Anonymous Therapist of Respiratory Therapy 101 tells us such a story where family members added even more problems by their presence.

Sometimes, changes to the worse follow a seasonal variation. Allergy Notes tells us why children with asthma get sick in September.

Changes to the better

Lisa who lets us follow her Cushing's Disease Journey is very happy to report a dramatic improvement after surgery which has turned her whole life to the positive.

The same is true for Rachel. In her Tales she lets us know about a sudden change in work environment.

Even everyday movements may be subject to positive change, that is, to a healthier way. For instance, do you know how to gaze at meteors without doing harm to your neck? Jolie Bookspan, the Fitness Fixer, tells you how to do it the healthy way.

And do not forget all these technical gadgets! They are being improved all the time. For instance, Amy Tenderich of Diabetes Mine is quite enthusiastic about a new glucose meter that is combined with a cell phone.

Not so sudden changes

Aman runs a Technology, Health and Development blog and has submitted the first time ever to a carnival. Welcome him and watch his report on a slow but important increase of health reporting in the business press.

Important changes are not necessarily sudden changes. Teri Polick shows us such a case at Nurse Ratched's Place: The slow but huge changes in nursing practice over the past decades.

Pregnancy is one of the most natural examples of a slow change. Tara Gidus, serving advice on her Diet Dish Blog, tells more about the subtle changes and the dos and don'ts in pregnancy.

Alvaro Fernandez of Sharp Brains warns us about the slow but substantial trend in ageing workforce and the importance of keeping their brains fit.

A very slow, sort of glacial change is reported by David C. Harlow in his HealthBlawg: The Centers for Medicare & Medicaid Services (CMS) are moving in the direction of payment for performance, an important trend in healthcare insurance.

Another slow but important trend is towards Consumer Driven Health Care: Retail-based clinical models may provide better care for lower cost, as Henry Stern in his InsureBlog points out and asks why the AMA is still in opposition to such such models.

Virtual changes

second life
There are people like me who have one life. And there are people like Bertalan Mesko who have two lives. At Scienceroll, he shows us how his double ego at Second Life has come together with a couple of other participants for the first medical simulation. Second life, according to Clinical Cases, is one of six important elements of Web 2.0 in medicine.

Blogs are also such an element. Hsien of Eye on DNA every now and then makes sudden changes of authorship by interviewing other bloggers and, like this time, by inviting guest bloggers. Don't miss Sarah Ost's guest post about ethical guidelines for health bloggers and consider, like me (as soon as I have more time, cross my heart) to join the Healthblogger Code of Ethics.

Will emails become an important communications tool between patients and physicians? Joshua Schwimmer at Tech Medicine discusses the requirements that must be met.

If you want to quit smoking, is it better to make a sudden change or to reduce gradually? Jonathan Foulds at Freedom from Smoking discusses the pros and cons of both ways.

Trisha at Ideas For Women has a more global scope of the problem and muses about what should be done.

Increasing tobacco taxes is a plan favoured by Jon Schnaars of Treatment online.

Many plans that are yet far from reality are hatched in the labs all over the world. GrrlScientist at her Scienceblog reports about a bone hormone that may help against obesity and diabetes in the future.

Bird flu is a case where we all hope there will never be a sudden change at all as long as the bug keeps quiet. But at the vax front, a change is badly needed for being prepared against a pandemic. InsideSurgery has an interview with noted bird flu vaccine researcher Dr. James Campbell.

A piece of science fiction that may turn reality by 2009 is told by Steven F. Palter at docinthemachine: A battlefield robot surgeon. I'd rather prefer not to send soldiers to war.

Some things never change? (Hope dies last!)

blood diamond
Si verräbled det une! If we Swiss get emotional, we cannot help saying it in Schwyzerdütsch. Sorry, I have to repeat: They are croaking down there! Be well prepared because it is hard stuff that Bongi of Other Things Amanzi tells us: The shocking story of bureaucrats that hassle a doctor until his patient is dead. A must read for all of us others who have the privilege to live in a better world.

Did you think that bad hand washing of doctors is a problem of the past? You are wrong. Tiny Shrink knows better. At Why am I still here, she tells us why doctors still do not wash their hands.

When it comes to science in general and to genetics in particular, I can be a hard fighter against religion. But on the other hand I have a deep respect for people like Susan Palwick who meet the spiritual needs of people suffering from serious disease or approaching death in a hospital. In her blog, Improbable Optimisms, she deals with the role of spirituality in the age of evidence-based medicine.

Type 1 diabetic Kerri Morrone, about to mark 21 years with the disease and blogging at Six Until Me, realizes that while she doesn't count on a cure, she still remembers how to hope. A great post that brings us back to where this edition has begun: If we cannot change things, we always can change ourselves.


This concludes volume 3, number 47. I am indebted to all who have submitted these wonderful posts and to Nick Genes for maintaining Grand Rounds. Also he has interviewed me for his Pre-Rounds column at Medscape. If you have missed Hsien's beach house edition, visit it at Eye on DNA. Next edition will be hosted by Med-Source.

It has been my great pleasure to be your host. I hope you enjoyed my presentation. And may things change to your best or stay if they already are.

Heartbeat curve by Crescendo

Monday, August 13, 2007

Public health expert backs my view on weight loss

Dr. med Francois van der Linde
I have asked Dr. François van der Linde, former Public Health Officer of the Swiss canton St. Gall, to comment on my post «The day when I stopped to believe in weight loss». This is what he just told me in a phone call.

He shares my view that the war on obesity may do more harm than good. He strongly warns against making public recommendations on nutrition and weight loss without a firm scientific base. We know too little about the real causes of the so called «overweight epidemic» to do so. He also is not convinced that the limit of body mass index 25, where overweight officially begins, makes sense, at least not for the general population. Advice on nutrition and body weight management should always be aimed at individual persons and not at the general population.

On the other hand, he warns me against falling into the other extreme and ignore negative health effects that still may be linked to obesity. This is exactly my own view, I replied: I am not going to fall from one religion to another. Rather I have turned from believer to agnostic, and I am going to have a special focus on studies that may show possible direct negative health effects of body fat as such.

Saturday, August 11, 2007

The vital importance of body fat

stone age live
A very interesting experiment is running in Switzerland these days. Ten persons, two families and two single young men, selected by a casting of Swiss Television, have been transferred to stone age. In a piece of natural landscape, carefully shielded from civilization (except air traffic noise), a small stone age village has been reconstructed. The participants have been equipped with all the tools, clothes and foods that had been in use more than five thousand years ago in Switzerland. The new stone agers have been living there for three weeks now, under constant monitoring not only by Swiss TV but also by medical experts.

All participants are equipped with motion sensors that allow to calculate the daily energy spending in kilokalories. The weights of all participants are also monitored and all data will be evaluated by scientists. Two young men have left the village more than two weeks ago for a business trip to the alps. Their job is to provide the village with salt that has to be transported in a leather bag from a mine, more than three hundred kilometers (200 miles) away. Now they are on their way back.

beat villiger
Head physician of the project is Dr. Beat Villiger, Chief Medical Officer of the Swiss Olympic Team and a very distant in-law of mine. Yesterday I have watched his medical interim report. The two young men spend four and five thousand kilokalories every day. One has lost more than four kilograms (8 pounds), the other more than seven kilograms (14 pounds) of body weight. Those who have stayed in the village spend much less energy but still about double the amount that they have spent in modern life prior to their time trip to stone age.

The weather is quite cold and rainy these days. The fireplace has sunken into mud. One of the two adult women said that the cold is her most serious problem. The mere idea that I could have been there makes me shiver from cold. I am thin, and I think I just have too little body fat for living in stone age.

The good sides of body fat

Body fat has three main advantages that had once been very important for mankind: Under the skin, it helps to isolate the body against cold. It provides an energy reserve for long trips because even pemmican cannot provide the body with all the energy needed for extreme performance. And it helps to survive a starvation period.

In tens of thousands of years of evolution, the human organism has adapted to optimal management and storage of energy in the form of body fat. In the light of this long history of survival success it is hard to believe that body fat as such, even in amounts of obesity, can have a negative effect on health.

And where are the bad sides?

We all know that an unhealthy lifestyle can make people fat. We know also that they may get sick and die earlier. I think we should blame it on the unhealthy living. But I'll watch medical journals for every new study that may blame the body fat directly. I am very curious if I'll find one in the weeks and months to come. You can be sure to find it posted here. Stay tuned!

Photo credit:

Friday, August 10, 2007

Musings on a cod diet diabetes trial

Would you like to eat cod every day for four weeks? No beef but cod. No poultry but cod. No veal but cod. No milk and no cheese but cod. No breakfast eggs but cod. I would like to see your face at the end of the four weeks. I would like to ask you if you know this Monty Python sketch «Spam, spam, spam... ».

Exactly this sort of diet has been tested in a diabetes trial: Nineteen persons suffering from insulin resistance, a stage of pre-diabetes, have been divided in two groups. One group ate the cod diet for four weeks, the other group ate lean beef, pork, veal, eggs, milk and milk products. Both diets were designed to differ only in protein source but not in the amount of total protein, saturated and unsaturated fats. After four weeks, both groups switched to the other diet for another four weeks. In both periods, the reaction to insulin has been monitored in all persons. During the cod diet period, this reaction (sensitivity) has been better than in the control period. The study authors conclude: «Dietary cod protein improves insulin sensitivity in insulin-resistant individuals, and thus could contribute to prevent type 2 diabetes by reducing the metabolic complications related to insulin resistance.»

I have a problem with such diet trials. They always have to be extreme in order to get a statistical significance. Yes, cod will reduce the danger of diabetes if you eat cod and no other animal protein every day. But what if you decide, like me, that diets suck and that cod is fine, from time to time? Will it still be helpful against diabetes? I guess it still would, but I guess also that this contribution would be so tiny that it would no longer be detectable in a trial.

There is more than diabetes ...

All the same I see some value in such studies. The reason is simple. Diabetes is not the only disease that must be prevented. There are hundreds of other diseases, and against some of them cod may also be beneficial. Let me guess that against six more diseases a preventive cod effect of similar size may be found. If you add these effects, you may get a notable overall advantage with one or two cod servings a week.

... and there is more than cod

A second reason may be even more important. Diet studies are undertaken with dozens of food components. You find studies on the preventive effect of apples, garlic, milk, cheese, strawberries, chocolate, coffee, green tea, black tea, wine, nuts, fish oil, olive oil, whole grain, mineral water - if I would dig my memory and do some searches, I could cite many more here.

My advice is simple. Most important is what you like. But you may not know all foods that you will possibly enjoy. If you never eat cod and find a study that favours cod, just take it as a hint. No cod diet, beware. But give it a try and see if you like it. I guess that there is also a placebo effect in food: If you know it does good and if you like it, you will enjoy it even more.

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Thursday, August 9, 2007

Sex partners: Why do men report more than women?

Today I have come across a new study on sexual behaviour of students in Spain. I am not particularly interested to know how much contraception they use. But I am always curious to learn what number of partners are reported by men and by women. And really, just as suspected: Men report more partners than women in this study (no numbers given in the abstract).

In need for more data, I started a keyword search and found that adult men on average report 5 and women only 3.4 partners in Finland. In Norway, 29 percent of men but only 23 percent of women report extramarital affairs. Always this gender difference that I recall from many sex studies I have seen earlier.

Common sense tells me that the real numbers in heterosexual partners must be equal on average: Sex is (normally) an affair between one man and one woman. Therefore, every single sex affair must increase the partner score by one in a man and also by one in a woman. So how come all these differences? Two explanations are possible. Men lie (exaggerate) and women lie also (downplay) when reporting the number of their partners. Or the groups of men and of women are not representative for the whole population.

Boasting and downplaying

One main source of the difference is most likely that the desire for multiple partners is greater in men than in women, as a study in Ohio has shown. If the desired number is not the actual number, a man or a woman may be tempted to «adjust» the report in the desired direction. This is only human. In fact, I have found another Ohio study that supports this view: Men, after having been told that women are more permissive nowadays, reported more partners when they have been interviewed by a woman versus a man.

The role of prostitutes

But can dishonesty explain the whole difference? Possibly not. I always have asked myself to what extent prostitution may contribute. Men, as a part of their boasting strategy, may include prostitutes in their number of partners. But prostitutes are very unlikely to show up as subjects in a study. This might easily explain quite impressive discrepancies in the reported numbers. And really, after some scrolling down the search hits, I have found a study that supports this view.

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Wednesday, August 8, 2007

Vaccine, autism and statistical nonsense

Okay, it had to happen some day, and it happened yesterday: I came across a new study on thimerosal and autism. My first intention was to leave it aside because others, like Orac, have followed the controversy for a long time and have posted book chapter size posts about the subject: Read more at Respectful Insolence on Autism.

Just in brief for all to whom this is new: Thimerosal (thiomersal), a mercury containing preservative agent in vaccines until 2001, has been blamed to increase the risk of autism in children but the studies cited by the anti-vaccine activists do not really support such a view: Read more about the thiomersal controversy.

Now to the study I have found. Fifty-three patients with autism spectrum disorder (a broader definition of the disease, leading to more cases than autism in strict sense) have been examined. 28 percent of their mothers are rhesus-negative and have received a vaccine that prevents a serious, life-threatening illness of the baby. In a general population not affected by autism, the amount of rhesus-negative mothers is only 14 percent. In other words: Compared to non-autists, patients with autism spectrum are twice as likely to have a rhesus-negative mother and therefore have twice as likely been exposed to the thiomersal containing vaccine. The study authors conclude:

«The results provide insights into the potential role prenatal mercury exposure may play in some children with ASDs.»
Where the statistical nonsense begins

Nothing can be said against this statistics as such, and the conclusion is at least worth to be discussed. But there are two main sources of nonsense that may be drawn from this result. The first one is to conclude that it is necessarily the mercury and to jump from correlation to cause. The second one is to focus only on the double relative risk of autism without taking into account the absolute risks of (a) autism and (b) life-threatening disease of the newborn.

It can be the mercury, but ...

A fetus of a rhesus-negative woman may be exposed to
  1. Mercury from the vaccine.
  2. Immunoglobulines that are the main content of the vaccine, preserved by the mercury-containing agent.
  3. Substances produced by the pregnant woman as a reaction to the vaccine.
  4. If the fetus is rhesus-positive, the effect of the vaccine may not suppress the maternal antibody reaction by a hundred percent. The fetus will be exposed to some of these antibodies.
Absolute risks must be compared

As said before we should not jump to the conclusion that mercury doubles the risk of autism. But I need this hypothesis for my next calculation:
  1. In the United States, about one in 250 persons suffers from autism, that is 0.4 percent of the population. (Source: Fighting Autism). I have not found any figures about the spectrum, so let me be generous and assume that one percent of the population is affected. Let me also assume that mercury doubles the risk, thus causing one additional case in every hundred babies.
  2. Rhesus factor D (the dangerous part of it) is dominant, therefore a baby from a rhesus-negative mother will most likely be positive. I am not a genetics specialist so let me again be generous and assume that only fifty of every hundred babies will be positive and therefore threatened by the antibody reaction of the mother.
Now let's do some math. If we have vaccinated a hundred pregnant women, we may have caused one case of autism spectrum disorder. If we did not vaccinate, we may have caused fifty babies suffering from a life-threatening disease. The ratio of benefit to harm is fifty to one. And this is a very conservative estimate. Any questions left?

All other vaccines are different

After having settled the case of rhesus vaccine, what about MMR and all the other vaccines? Most of them never contained thiomersal. And against the tiny rest, this rhesus study does not add a scrap of new evidence. Just because it is a major difference between an exposed fetus and an exposed child. While I can imagine mercury doing some harm to the developing brain of a fetus in certain sensible stages, this is very unlikely to happen to the fully functional brain of a child.

The source of statistical nonsense

I do not blame the study authors. Their statement is correct. But such a study is very likely to be wrongly cited by anti-vaccine activists. Just wait until the media take up the story. I already see a science editor sit at his desk, creating a catchy headline such as «vaccine doubles autism risk, study shows». But if you, dear reader, happen to be a lawyer of parents of autistic children in a class action suit, forget it. This is not a corpus delicti.

Photo credit:

Judy of Tiggers don't Jump tells me I have missed an important point: Since 2001 there is no thiomersal at all in the vaccine (Rhogam). Thanks Judy, I forgot to mention that all subjects of the study have been born before 2001 and that all mothers have been vaccinated with the old product.

Monday, August 6, 2007

Stroke symptoms alone may harm

It is important to know the five most important stroke symptoms. Do you know them? If you haven't done my Stroke Health Quiz yet, you may scroll down or click here. Or, if you feel to need all the information right now, go directly to the solutions page where you find all the details together with links to more informations about stroke.

Two main groups of stroke symptoms

To sum up, one group of stroke symptoms involves sudden numbness and weakness of the body and another group involves sudden head and brain symptoms. The sudden occurrence is an important point. But not in every of such cases a stroke can be diagnosed. Apart from so-called «silent strokes» without any symptoms, the contrary may be true: Stroke symptoms that are not really strokes. Often a transient ischemic attack or mini-stroke can be diagnosed in such a case.

But not always. There is still a number of persons with stroke symptoms that do not lead to any diagnose. Such symptoms alone cause about half the amount of harm as a stroke, according to a study of the University of Alabama. The physical and mental performances have been assessed after various types of stroke symptoms and diagnoses.

In cases where no stroke has been diagnosed, two kinds of declines have been observed, depending on the kind of stroke symptoms. After symptoms affecting the body, the physical functioning is impaired. After head and brain symptoms, a mental decline can be observed.

Take home message: Stroke symptoms always must be taken seriously, even if no stroke can be detected.

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