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Overweight and risk of stroke

(September 2003)

Between 55 and 60 percent of American adults are overweight. That results in increased risk for diabetes, high blood pressure, elevated blood cholesterol levels, heart attacks, and certain cancers. There are now also multiple studies on risk of stroke in overweight individuals. Results from the Physicians’ Health Study are reported in the December 9, 2002 issue of the Archives of Internal Medicine; the investigators followed 21,414 men for twelve years. During this period, there were 747 strokes, the majority due to reduced blood flow to the brain. The doctors were divided into five groups according to weight categories. The measurement used was the body mass index (BMI) - the weight in kilograms divided by the square of the height in meters.

Those about 10 to 19 percent overweight (BMI 27 to 29.9) had a 50 percent increased risk of stroke; for those at least 20 percent overweight and considered obese (BMI 30 or over), the risk was doubled.

A considerable part of the increased risk was related to the hypertension caused by the overweight or obesity, but the authors insisted that overweight or obesity by themselves can cause strokes.

Commentary: The number dying from strokes in the United States has dropped dramatically in the last four decades, in large part because of better control of high blood pressure. Still, strokes are one of the leading causes of death. It is also well known that, if the overweight or obesity causes high blood pressure or diabetes, that will increase the risk of stroke. Despite this study, it is not clear whether overweight or obesity by themselves increase the risk of stroke. About one-half the studies show a relationship, one-half do not.

Two other studies from Harvard groups showed no increased risk at all for women (nurses) and an increased risk in men only for those who were obese, not for those who were overweight (BMI 25 to 29.9), but not obese.

Because the risk for obese persons in this study was doubled, it would be important to know whether that risk was found equally in both those with mild obesity (BMI 30 to 34.9) and in those with substantial obesity (BMI 35 and over). It would also have been useful to know whether any increased risk among overweight or obese men occurred only or primarily in those with abdominal obesity (waist circumference more than 40 inches). It has long been thought that a big gut (abdominal obesity) is a risk factor for stroke.

for whether overweight or obesity by themselves (in the absence of high blood pressure or diabetes) increase the risk of stroke.

This study leaves important questions unanswered, including whether general overweight in the absence of abdominal obesity increases stroke risk. Still, it is clear that, health-wise, it is better to be normal weight rather than moderately (up to 20 percent) overweight and better to be moderately overweight rather than more than 20 percent overweight (obese).

Kurth, T., et al. Body mass index and risk of stroke in men. Archives of Internal Medicine. Vol 162 (December 9) Pgs 2557-2562. 2002.

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