Study Finds Abdominal Obesity A Stroke Risk Factor

A new study by Columbia researchers indicates that people with abdominal obesity are at higher risk of ischemic stroke, the most common type of stroke, caused by blockage or constriction of a blood vessel in the brain.

Obesity is a known risk factor for coronary heart disease. But the connection between obesity and stroke has been murky because of conflicting results from studies that used body mass index, an overall indicator of obesity that is based on a ratio of weight to height. (One of the flaws of body mass index as an indicator is that it wrongly identifies shorter but muscled people as overweight because the measurements only consider overall size rather than proportions.) To achieve a more precise measurement of obesity, the researchers in this study used abdominal obesity measures, based on a ratio of waist circumference to hip circumference, according to one of the researchers, Dr. Ralph L. Sacco, professor and associate chairman of neurology at P&S and professor of epidemiology at the Mailman School of Public Health.

In a study of northern Manhattan residents, funded by the National Institute of Neurological Disorders and Stroke, the researchers compared 576 people with ischemic strokes to 1,142 people without strokes. Those with strokes were matched by age, gender, and race-ethnicity to those without strokes to enable better comparisons. The study population was 26 percent African-American, 55 percent Hispanic, and 17 percent white. The study's findings, published in the July issue of Stroke, are derived from the NIH-funded Northern Manhattan Stroke Study that has been ongoing since 1990.

The researchers found that abdominal obesity – even after adjusting for other stroke risk factors such as high blood pressure, diabetes, high cholesterol, smoking, cardiac disease, moderate alcohol consumption, and physical activity – is associated with a greater risk of stroke in men and women in all race and ethnic groups.

Abdominal obesity carries the highest risk for people under age 65 – an important finding since the rates of obesity in younger people continue to rise, Dr. Sacco says. Extra abdominal weight is also more risky for blacks and Hispanics, who have higher rates of stroke than whites.

Dr. Sacco also addressed the issue of controlling risk factors for stroke among African-Americans in an editorial that appeared in the June 11 issue of the Journal of the American Medical Association. Dr. Sacco lauded a study in the same issue that found aspirin slightly more effective in preventing recurrent stroke in black patients than ticlopidine, a more expensive, antiplatelet medication. However, he added that much more needs to be done to prevent the high rates of stroke among African-Americans.

Dr. Sacco said the research, led by investigators at Rush Medical College, is an example of a "focused, hypothesis-driven, randomized treatment trial" that is noteworthy both for its findings and because the researchers worked hard to enroll more than 1,800 black men and women – the largest study of stroke among black patients to date. Often, black people are under-represented in clinical trials, making it more difficult to decipher why they are more susceptible to strokes. The rates of stroke and death from stroke are about twice as high for blacks as for whites.

The latest study comparing ticlopidine to aspirin was undertaken because a 1993 study – which enrolled only a small number of black people – showed ticlopidine had fewer side effects and greater benefits than aspirin for non-whites. However, based on the new study's findings, aspirin is seen as an attractive option for preventing recurrent strokes because it is readily available, easy to use, relatively safe, and much less expensive than other major anti-platelet agents.

Better approaches are needed, Dr. Sacco says, to reach communities of lower socioeconomic status, where residents often are less educated about the significance of risk factor control and have less access to healthcare to identify and manage risk factors.

"There is a lot more we need to do besides giving a drug to people," Dr. Sacco says. "We need to control stroke risk factors such as high blood pressure, diabetes, obesity, and encourage cholesterol reduction in blacks and especially in black stroke survivors."