Objective: To examine the effects of giving up smoking, years since quitting smoking and the quantity of cigarettes smoked, and primary pipe or cigar smoking on the risk of stroke.
Design, subjects, and setting: A prospective study of cardiovascular disease and its risk factors in 7735 men aged 40 through 59 years drawn at random from the age-sex registers of one general practice in each of 24 British towns from 1978 through 1980 (the British Regional Heart Study).
Main outcome measure: Incidence of fatal and nonfatal major stroke events (strokes) during an average follow-up period of 12.75 years.
Results: During the 12.75 years of follow-up, there were 167 major stroke events (43 fatal and 124 nonfatal) in the 7264 men with no recall of previous ischemic heart disease or stroke. After full adjustment for other risk factors, current smokers had a nearly fourfold relative risk (RR) of stroke compared with never smokers (RR, 3.7; 95% confidence interval [CI], 2.0 to 6.9). Ex-cigarette smokers showed lower risk than current smokers but showed excess risk compared with never smokers (RR, 1.7; 95% CI, 0.9 to 3.3; P = .11); those who switched to pipe or cigar smoking showed a significantly increased risk (RR, 3.3; 95% CI, 1.6 to 7.1) similar to that of current light smokers. Primary pipe or cigar smokers also showed increased risk (RR, 2.2; 95% CI, 0.6 to 8.0), but the number of subjects involved was small. The benefit of giving up smoking completely was seen within 5 years of quitting, with no further consistent decline in risk thereafter, but this was dependent on the amount of tobacco smoked. Light smokers (< 20 cigarettes/d) reverted to the risk level of those who had never smoked. Heavy smokers retained a more than twofold risk compared with never smokers (RR, 2.2; 95% CI, 1.1 to 4.3). The age-adjusted RR of stroke in those who quit smoking during the first 5 years of follow-up (recent quitters) was reduced compared with continuing smokers (RR, 1.8; 95% CI, 0.7 to 4.6 vs RR, 4.3; 95% CI, 2.1 to 8.8). The benefit of quitting smoking was observed in both normotensive and hypertensive men, but the absolute benefit was greater in hypertensive subjects.
Conclusion: Smoking cessation is associated with a considerable and rapid benefit in decreasing the risk of stroke, particularly in light smokers (< 20 cigarettes/d); a complete loss of risk is not seen in heavy smokers. Switching to pipe or cigar smoking confers little benefit, emphasizing the need for complete cessation of smoking. The absolute benefit of quitting smoking on risk of stroke is most marked in hypertensive subjects.