14-year study finds that quitting smoking adds years to life

Participants who quit had a 46% lower death rate

In a new study of 5,887 middle-aged smokers with mild lung disease, those who were randomly assigned to a quit-smoking program had a lower death rate than those assigned to usual care, even though only 21.7 percent of them actually quit smoking.
The annual death rates were 8.8 per 1000 participants in the quit-smoking program and 10.4 per 1000 in the usual care group. The annual death rates for those who actually quit was even more positive: 6.0 per 1000 patients compared with 11.0 per 1000 in those who did not quit smoking. Overall, the death rate of those in both groups who were able to quit smoking was 46 percent lower than those who did not quit.

The study, “The Effects of a Smoking Cessation Intervention on 14.5-year Morality,” is the first experimental study to show that stopping smoking adds years to life. It is published in the Feb. 15, 2005, issue of Annals of Internal Medicine. The findings were based on data from the Lung Health Study. Randomized trials like the Lung Health Study are widely regarded as the gold standard for proof among clinical studies. “We know that people who smoke should quit smoking,” said one of the study authors, John E. Connett, PhD, professor of biostatistics of the University of Minnesota School of Public Health. “This study showed that with very simple lung function tests — spirometry — we can find people who can benefit the most from an intensive quit-smoking program,” Connet said. “And it not only made them healthier and feel better, it caused substantial reductions in death rate.”

The participants in the study all had mild lung disease, which itself increases risk for more serious lung disease down the road. In an editorial, “Smoking Kills, Experimental Proof from the Lung Health Study,” Jonathan M. Samet, MD, MS, of the Johns Hopkins Bloomberg School of Public Health, says that the importance of the new findings is that the study was randomized and was large enough and long enough to truly test whether smoking cessation reduces all-cause mortality. Previous studies linking smoking to death from specific diseases, such as lung cancer and heart disease, were based on observation rather than on experiment. These new findings “prove that smoking causes increased risk for death in smokers,” Dr. Samet said in the editorial. “No one can make a serious claim to the contrary in light of this randomized trial evidence.”

A surprising finding, according to Dr. Connett, was that the reduction in death rate was more significant in younger people, 35 to 45, than older people. “Current guidelines suggest that smokers over age 45 should be screened, but our study found that younger people have more to gain from being screened than older people,” Connett said. “Young people who are found to have abnormal lung function should be put into an aggressive quit-smoking program.”

Dr. Connett commented on the unusual study finding that even those who did not quit smoking completely had lower death rates than the people who continued to smoke throughout. “One might have thought that this program was not working, because by most standards, only 20 percent or so of the people who were enrolled in it quit smoking continuously,” Connett said. “People quit, restarted, and quit again. However, quitting had such a statistically large impact on the overall population that even though many people quit and started smoking again, as long as they were smoke-free for periods of time, they had better outcomes than those who continued to smoke.”