U.S. and Canadian researchers have shown that middle-aged people who were helped to quit smoking for good were less likely to die over the next 15 years or so.

In particular, people who successfully quit were significantly less likely to die from lung cancer and cardiovascular disease, the investigators report in the Annals of Internal Medicine.

“Smoking shortens your life expectancy, and quitting smoking - even after years of being exposed to cigarettes - can help you live longer and feel better,” Dr. John E. Connett told AMN Health.

There are many reasons why smoking shortens lifespan, he explained. For instance, smoking causes chronic inflammation in your lungs and airways, resulting in coughing, shortness of breath and wheezing, which stresses your system.

Smoking also forces the heart, blood and cardiovascular system to work harder to maintain your body’s functioning, he noted. Finally, cigarette smoke contains substances that can cause cancer, Connett said.

“Quitting smoking reverses many of these effects,” he noted.

In the report, Connett and his team write that this is the first study of its kind to quantify the years people regain from quitting smoking. As part of the study, Connett and his team asked two-thirds of 5,887 middle-aged smokers to participate in a 10-week program to help them stop smoking, then followed them for nearly 15 years, noting who died.

As part of the intervention program, smokers attended 12 group sessions and used behavior modification techniques and nicotine gum to quit. Smokers did not consider themselves to be sick, but all had signs of lung obstruction.

Five years after the program, 22 percent of smokers who attended the intervention program had quit, compared with only 5 percent of people who didn’t try the intervention.

“The death rates in people who quit were reduced, and strikingly the reductions were not concentrated in one area, but were spread across in several different common causes of death: cardiovascular disease, non-cancer respiratory diseases, lung cancer, and other causes,” Connett said.

In an accompanying editorial, Dr. Jonathan M. Samet of Johns Hopkins Bloomberg School of Medicine in Baltimore, Maryland writes that this study helps demonstrate that smoking itself is the reason smokers live shorter lives than non-smokers, on average. “No one can make a serious claim to the contrary in light of this” study, he notes.

SOURCE: Annals of Internal Medicine, February 15, 2005.