Smoking fewer cigarettes may not have much effect on a person’s life span

THE QUESTION Though smokers generally have a shorter life expectancy than nonsmokers, might cutting back on the number of cigarettes allow a smoker to live longer?

THIS STUDY involved 5,254 smokers, in two separate groups, who were 40 to 65 years old at the start of the study. During roughly the next 30 years, 4,439 of the participants (84 percent) died. Those who quit smoking after the study began were more likely to live to at least age 75. They also were 25 to 35 percent less likely than the others to have died. But there was essentially no difference in the mortality rate for people who had reduced the number of cigarettes they smoked daily and those who had continued smoking at the same rate. The only participants to see any benefit from reducing the number of cigarettes smoked were the heaviest smokers (more than 21 cigarettes a day) in one of the two groups; their mortality rate improved when the number of cigarettes they smoked daily was reduced.

WHO MAY BE AFFECTED? Anyone who smokes. About half of all smokers die of smoking-related problems, and chronic smokers can expect to die about 10 years earlier than nonsmokers. Those who quit before age 40, however, can eliminate that reduction in longevity.

CAVEATS Data on smoking came from the participants’ recollections and were gathered twice, during the early years of the study. The data, therefore, do not reflect changes in smoking habits that may have occurred in later years. The study authors suggested that, despite the findings, cutting back on smoking could have “a potentially important role as a step toward smoking cessation.”

FIND THIS STUDY July 3 online issue of the American Journal of Epidemiology.

LEARN MORE ABOUT the health hazards of smoking, as well as how to quit, at betobaccofree.hhs.gov and www.cancer.org (click “Learn About Cancer,” then “What causes cancer?”).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.