Tuesday, October 30, 2007

Should we kill cholesterol, the bearer of bad news?

High cholesterol has been linked to heart disease and stroke risk in a big study but we should be careful with explanations and actions.

A study on cholesterol, diabetes and major cardiovascular diseases in the Asia-Pacific region included a third of a million persons whose blood cholesterol levels have been assessed and who have been followed up four years on average. Six thousand of them (1.8 percent) had a heart attack during that time. When linked to the cholesterol data, every one millimol per liter increase of blood cholesterol level was associated with a 41 percent higher relative risk of a heart attack. This may sound impressive, but it must be related to the absolute risk, therefore, the risk increase linked to cholesterol is a mere 0.7 percent. Nevertheless, the authors of the study conclude that

" (...) these data support aggressive lowering of total cholesterol and LDL-cholesterol levels for prevention of cardiovascular events."
That is, prescribing high doses of statin. Statins do in fact lower cholesterol levels but they have a couple of other effects, thus it remains unclear if their preventive action against heart attacks has anything to do with cholesterol. Other attempts, for instance low-cholesterol diets, have proven to be useless because the main amount of cholesterol is produced by the body who regulates its production up or down, according to the input.

Is cholesterol the culprit anyway?

In ancient times, bearers of bad news sometimes have been executed which was supposed to comfort the King but did not change the facts. Cholesterol may be regarded as a bearer of risk, if we think that 0.7 percent risk increase is really bad news. But cholesterol is not necessarily a cause of this risk increase.

A number of studies have shown that stress makes blood cholesterol rise and exercise makes it fall. Thus, stress and lack of exercise may be the real causes of heart attacks, and cholesterol levels may only be a side effect.

Interestingly, other studies have shown positive effects of high blood cholesterol levels - read more in my upcoming posts.

Related post: More statin may save lives after heart attack but so may red wine.

Photo credit: flickr.com/photos/streamofconsciousness/109783888/

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