Middle-age men who have high blood pressure and smoke more than 20 cigarettes daily are 10 times more likely to suffer a stroke than non-smokers with normal blood pressure, a new study says.

Smokers with normal blood pressure increase their risk of stroke 2 1/2 times compared to non-smokers, said Dr. Gerry Shaper, principal author of the study published in this week's British Medical Journal.Men who quit smoking had the same risk as non-smokers, Shaper, an epidemiologist at London's Royal Free Hospital, said in a telephone interview Thursday.

"That cigarette smoking is of considerable importance in stroke now seems undeniable," Shaper said. He said the best advice for people with hypertension is not to smoke.

Cigarettes seem to increase the risk of stroke by narrowing arteries and affecting the clotting process, Shaper said.

Shaper said that among 110 men who had strokes during the eight-year study, 98 smoked. Of 52 men who had a stroke before entering the study, half continued to smoke.

The regional study, which monitored 7,735 men between the ages of 40 and 59 for eight years, also found that heavy drinkers - who had more than three pints of beer or six glasses of wine a day - are four times as likely to have a stroke.

According to the American Heart Association, about 500,000 Americans suffer from strokes every year and 150,000 die, making stroke the third leading cause of death.