People who stop smoking can live a lot longer, regardless of the age at which they quit, according to a report in the American Journal of Public Health (Vol. 92, No. 6: 990-996).

The study found that younger people benefit the most, but even those who are 65 can add years to their life by quitting.

"What's unique about this study is that it gives some hope even to 65-year-olds who smoke," said Donald Taylor Jr, PhD, at Duke University in Durham, N.C. "A man would add between 1.4 and 2 years to his life. That's a tangible benefit you can get even late in life from stopping smoking."

According to the study, women who were 65 years old added nearly four years to their lives when they quit, compared to smokers.

But the greatest benefits were seen by the youngest people in the study. Smokers who quit at age 35 could expect to live up to eight and one-half years longer than continuing smokers.

In order to calculate the benefits of quitting, researchers looked at responses from 877,243 people in the American Cancer Society's (ACS) Cancer Prevention Study II and at data from the 1990 US census. They compared data on smokers, former smokers, and those who had never smoked.

The study used a national and much larger sample than previous studies, and found a much higher benefit for stopping smoking by middle age.

"The size of the life extension is pretty big," said Taylor.

"Everybody's probably got a pretty good idea that smoking is bad for you," he said. "Since the 1950s, smoking prevalence has fallen quite a bit, but it's flattened out in the past 10 years. I think part of what we need to do is to provide messages that provide the benefits of quitting in an understandable way."

According to the ACS, tobacco use is responsible for one in five deaths in the US. With 47 million smokers in the US, the message that it's never too late to quit is an important one, said an ACS expert.

"Probably the single most important thing that someone can do for their health is to quit smoking," said Ron Todd, MSEd, director of tobacco control at the ACS.

"The messages from this study that I think are important are the simpler ones. There are great benefits to be derived from quitting smoking regardless of your age, but the benefits are even greater the earlier you quit," he said.

Todd said smokers who have tried to quit in the past and haven't been successful are actually the ones who succeed in the long run.

"The people who continually aspire to quit and make repeated attempts are the ones who eventually stop and quit permanently," he said. "It's very important to continue to try to stop smoking."