By William J. Cromie

Gazette Staff

Extra weight significantly raises the risk that a woman will suffer the most common type of stroke, say Medical School scientists.

Females who are more than 20 percent over their recommended weight, or who have gained more than 44 pounds since age 18, more than double their risk of suffering a stroke, compared to leaner women. Even a gain of between 22 and 44 pounds since her teen years makes a middle-aged woman almost twice as likely to experience a stroke, or brain attack.

"Obesity, especially in women, continues to be a serious epidemic in this country and now there is strong evidence of yet another health risk for overweight women," says Kathryn Rexrode, an instructor in medicine at Brigham and Women's Hospital. An estimated one-third of all women in the United States are obese, or at least 20 percent overweight.

"A number of studies have shown that the risk of stroke in men increases with obesity," notes Charles Hennekens, Eugene Braunwald Professor of Medicine. "Up until now, studies of women have been inconclusive. Some researchers found a link, some didn't. This latest study is the largest and most conclusive to date."

Another Harvard study, published two years ago, found that women who gain 22 pounds or more between age 18 and middle age raise their risk of death from heart attack and cancer. "Deaths from heart and blood vessel disease were substantially higher among obese women," notes JoAnn Manson, associate professor of medicine, who participated in the 1995 study and in the current one on stroke.

Rexrode, Hennekens, Manson, and their colleagues examined questionnaires filled out over a 16-year period by 116,759 registered nurses. The study documented 866 strokes among these women. The analysis "provides evidence that weight gain and obesity are significant risk factors for ischemic and total stroke, but not hemorrhagic stroke," Rexrode says.

Ischemic stroke accounts for about 80 percent of all strokes and is caused by blockage of a blood vessel in the neck or brain. A hemorrhagic brain attack results from a ruptured blood vessel in the brain. Total strokes involve a combination of both.

Too Much Body Mass

As a measure of obesity, researchers use a combination of height and weight called the body mass index (BMI). It is determined by multiplying weight in pounds by 0.45 to convert it to kilograms. The weight then is divided by height in meters squared, or multiplied by itself. A 5-foot-6-inch woman or man weighing 150 pounds has a BMI of 25, which carries no added risk of stroke.

But a 5-foot-6-inch woman who weighs 165 pounds has a BMI of 27 and that raises her risk to 1.7 times that of those with a BMI less than 21. She would have to drop to 126 pounds to reach a BMI below 21.

A 5-foot-6-inch woman weighing 194 pounds would be severely obese with a BMI of 32. She would be more than twice as likely to suffer a stroke.

Harvard researchers have also found that women with a BMI between 29 and 32 double their relative risk of death from all forms of heart disease. Those with a BMI of 32 triple their death risk from heart disease and double it for cancer and other causes.

For stroke, women who gain 22 to 44 pounds from age 18 to middle age increase their risk 1.7 times. Those who put on more than 44 pounds become more than two-and-half times as likely to have a brain attack.

According to the American Heart Association, about 228,000 females in this country suffer brain attacks, and 91,000 women die from them each year. Most of the strokes and deaths occur at age 65 or older.

Lean women apparently don't escape such risks if they smoke or have high blood pressure. Rexrode and her colleagues found evidence to suggest that such females are at higher risk for hemorrhagic stroke.

"There are many things women can do to help prevent stroke, including quitting smoking, keeping blood pressure down, treating diabetes, maintaining a healthy weight, exercising, and eating a balanced diet," Rexrode says.

The results of this study were published yesterday in The Journal of the American Medical Association.