A new study has found the flu vaccine may offer significant protection against stroke. If the finding is confirmed, the flu vaccine could turn out to be a valuable weapon in the fight against heart disease.

Hardening of the arteries, or atherosclerosis, is a common form of heart disease in which hard deposits form in blood vessels. One of the latest theories about how this contributes to stroke or heart attack is infection.

"We know some infectious disease may cause atherosclerosis plaque rupture, leading to thrombosis and occlusion of coronary arteries and brain arteries ? So, our hypothesis was if this is true, patients vaccinated against influenza may be at less risk for stroke," says Pierre Amarenco, a neurologist at Bichat Hospital in Paris and co-author of a study appearing in the February issue of the American Heart Association journal, "Stroke."

The investigators studied 90 patients admitted to the hospital's stroke center between December 1998 and March 2000. The researchers compared them to a control group of people in the general population, matching them for age, gender, and lifestyle factors. Both patients and controls were asked if they received the flu vaccine.

Among the general population, the researchers found there were no strokes, with a larger percentage of that group having received flu shots. Dr. Amarenco says the study suggests the vaccine could reduce the risk of stroke by as much as 20 percent. However, he's cautious about leaping to conclusions. "It is possible that the association we found is due to prevention of stroke. But it may also be that with the vaccination, we identified a group of patients at less risk of stroke because they have a better lifestyle," he says.

Dr. Amarenco and colleagues are going to try to confirm their results in a study of one thousand patients, to see whether vaccinating them against the flu actually reduces their risk of heart disease in later years.

A few years ago, no body would have thought that infections were a key risk factor for developing ulcers in the stomach. Low and behold, we now know they are," says Harold Adams, a neurologist at the University of Iowa. Dr. Adams is intrigued with the notion that flu vaccines can reduce peoples' risk of developing heart attack or stroke.

If you think that hardening of the arteries is very common in populations around the world, not just in the United States, but in Europe and in other parts of the world as well. And that there might be multi factors that led to acceleration of hardening of the arteries; dietary things, lifestyle things such as smoking. Why could inflammation or infection not play a role?

Interestingly, older patients in the study, those over 75, who had been vaccinated against the flu, showed no reduced risk of stroke. Experts say that could be because the immune systems of older people are less robust than younger individuals, and the vaccines may not have been as effective in the older participants.