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Wednesday, March 19, 2008

Obesity Paradox also Holds in Denmark

Regular readers of this blog will have noted previous entries on the "paradoxical" reverse epidemiology of obesity and cardiovascular mortality, where risk is apparently higher in underweight compared to normal weight, overweight or even mildly obese individuals (for e.g. of previous blog entries on this click here, here or here).

Now a new Danish study by Jawdat Abdull and colleagues published in the European Heart Journal that looks at pooled data from 5 large registries with over 21,500 consecutive high-risk patients with myocardial infarction or heart failure finds essentially the same story:

After a follow-up of 10.4 years, compared with normal weight individuals (BMI 18.5-24.9) all-cause mortality was higher in underweight (BMI < 18.5) but not in overweight (BMI 25.0-29.9) or class I obese (BMI 30-34.9) individuals. Only with class II obesity (BMI 35-39.9) and higher was there a significantly increased risk for myocardial infarction and increased death risk.

This finding is very much in line with the mounting evidence that moderate overweight and mild obesity does not automatically translate into higher cardiovascular mortality in high-risk individuals with established heart disease.

As argued before, given that increased weight is a well-established risk factor for high blood pressure, diabetes, and other risk factors for cardiovascular disease, the reasons for this rather consistent "paradoxical" relationship are not clear.

Possible explanations include the idea that being underweight is a sign of general ill health and that thin people may be less able to cope with life-threatening illnesses like a heart attack at least compared to people with some extra "nutritional reserve". Of course there are a couple of more sophisticated theories out there that to me appear highly speculative (which is why I will not mention them today).

Nevertheless, in light of this "paradox", we may have to look beyond reducing cardiovascular morbidity and mortality to justify aggressive treatments of overweight and class I obesity with established cardiovascular disease - perhaps the aim of obesity treatment in high-risk individuals should simply be to prevent further weight gain rather than to reduce it?

I guess it would take intervention trials to find out - thankfully, these are already well underway.


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