People who quit smoking by 40 may live as long as people who never smoked

Research has shown that smoking can chop at least 10 years off a person's lifespan. However, a new study suggests that smokers who quit before the age of 40 may be able to live as long as people who never smoked at all.

"Quitting smoking before age 40, and preferably well before 40, gives back almost all of the decade of lost life from continued smoking," Dr. Prabhat Jha, head of the Centre for Global Health Research at St. Michael's Hospital and a professor in the Dalla Lana School of Public Health at the University of Toronto, said in a press release.

About 46.6 million U.S. adults smoke cigarettes, according to the Centers for Disease Control and Prevention. Annually about 443,000 people die from smoking-related illnesses and another 8.6 million people live with a smoking-related disease.

For the study, which was published on Jan. 23 in the New England Journal of Medicine, researchers looked at data on health habits taken from the U.S. National Health Interview Survey and linked it to the National Death Index. Unlike previous studies on smoking and smoking cessation which used nurses or volunteers -- individuals who may be healthier than the average American -- the more than 200,000 people who participated in the survey were a nationally representative sample. About 16,000 of the survey responders died from smoking-related causes.

Overall, men and women who smoked lost about 10 years of their life. Current male and female smokers between the ages of 25 to 79 were three times more likely to die prematurely than those who had never smoked at all. Non-smokers were also twice as likely to live to the age of 80 compared to smokers.

Researchers also found that women's risk of dying from smoking-related causes was 50 percent higher than what studies completed in the 1980s found. Another study published in the New England Journal of Medicine on Thursday hypothesized that women's death rates are higher because they are starting to smoke at earlier ages and smoking more in general. That study showed that while men's lung cancer rates used to be much higher than women's, they had caught up.

The researchers found that people who quit smoking between the ages of 35 to 44 gained nine years back of life, while those who quit between 45 to 54 and 55 to 64 got six years back.

But Jha emphasized that the study isn't suggesting people can smoke until the age of 40 and then suddenly quit.

"Former smokers still have a greater risk of dying sooner than people who never smoked," Jha said. "But the risk is small compared to the huge risk for those who continue to smoke."

Dr. Graham Berlyne, a respirologist and chief of medicine at St. Joseph's Health Centre in Toronto, added to the CBC, "The years of smoking are not erased but the damage done is halted and the lungs have a huge capacity so that we can still function even having lost some capacity," Berlyne said.

Others point out that the study shows that smoking takes away a large chunk of your life, and that should be the main takeaway.

"If you don't smoke, you're going to live a longer life," said Margaret Bernhardt-Lowdon, tobacco-issues spokeswoman for the Canadian Lung Association told the Globe and Mail. She was not involved in the study. "It really makes it very clear when they're talking about having a 10-year less life expectancy."