NEW YORK (Reuters Health) – Quitting smoking decreases the risk of stroke and heart attack, but the benefits of just cutting down are less clearcut, according to study results published in the medical journal Stroke. Dr. Hong-Jun Cho, of the Asian Medical Center, Seoul, Korea, and colleagues assessed the effects of smoking reduction and cessation on the risk of fatal and nonfatal stroke and heart attack in 475,734 Korean men between the ages of 30 and 58 years who were enrolled in the Korean National Health Insurance System.

The subjects were classified into groups based on their smoking status at two time periods, 1990 and 1992. The nine groups included: heavy smokers (at least 20 cigarettes per day), moderate smokers (10 to 19 cigarettes per day), light smokers (less than 10 cigarettes per day), heavy smokers who became moderate smokers, heavy smokers who became light smokers, moderate smokers who became light smokers, smokers who quit, ex-smokers who remained abstinent; and individuals who never smoked.

By 2001, a total of 6,092 strokes and 2,164 heart attacks occurred. Participants who quit smoking had significantly lower risks of stroke and heart attack, about 40 and 60 percent lower, respectively, compared with heavy smokers.

Heavy smokers who reduced their smoking levels had lower risks of stroke and heart attack compared with heavy smokers. However, these reductions were not statistically significant.

Only a slight reduction in risk was seen in moderate smokers who reduced their smoking levels compared with moderate smokers who didn't change their habits or those who increased their smoking level, Cho and colleagues report.