Longevity wise, it’s almost like you never took a drag.

Butting out permanently before age 40 can restore the life expectancies of smokers to virtually normal lengths, shows a new study out of Toronto’s St. Michael’s Hospital.

“The survival curves become close to never-smokers,” said Dr. Prabhat Jha, head of St. Mike’s Centre for Global Health Research.

“You’re still at a disadvantage by quitting at age 40, but those that quit by age 30 have pretty much the same survival curves as never-smokers,” according to Jha, a public health expert at the University of Toronto whose study was published Wednesday by the New England Journal of Medicine.

Cigarettes statistically cut a decade off a smoker’s life, Jha said. But those who quit at 40 can gain back nine of those lost years.

Currently, life expectancies sit around 80 years for the large majority of non-smoking 25-year-olds in North America. Some 70 per cent of women and 60 per cent of men will reach their eighties.

Similar majorities of people who quit the weed at 40 can expect to live to 79, Jha said.

Such statistics, Jha concedes, will surely encourage some younger smokers to hang fire on quitting during their more reckless years.

“Yep” he said. But he quickly adds that such thinking would be lethal in many cases.

“That’s the wrong message, to say that it’s safe to smoke until age 40 and then quit,” Jha said.

First, he said, people quitting at 40 are statistically giving up a year of life that non-smokers would typically enjoy.

“You don’t get 10 years of life back, you get nine years of life back, so it’s not a trivial risk.”

Second, the longevity gains of quitting at 40 reflect precipitous drops in the risks those smokers face for factors such as heart attack and stroke, Jha said.

The chance that smokers will develop lung or other types of cancer remain higher and linger for years after they’ve butted out.

“Certainly for lung cancer, the damage will persist,” Jha said.

But the study holds good news for most smokers in its findings that quitting at almost any age can confer significant gains in life expectancy.

“The message really is (that) it’s best to quit as early as possible, but if you can’t, quitting at any age will have benefits,” Jha said.

“Even those who quit by age 50, they get back about six years of life. And if you quit even at age 60, you get four years of life back.”

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There’s bad news in the study, too. It explodes the long-held belief that women face fewer hazards from smoking than men.

“It ain’t true,” Jha said. “If women smoke like men, they die like men.”

The study scoured data from the massive U.S. National Health Interview Survey, which queries a broad cross-section of the American public each year on medical issues.

The researchers linked some 200,000 people from that survey to the U.S. National Death Index to tease out their smoking statistics.

Though the data is U.S.-based, Canadian Institutes of Health Research scientist David Hammond said the study would almost certainly reflect a similar situation in this country.

“It’s hard to think of any two countries that are more similar in terms of the tobacco markets and the historical smoking rates,” said Hammond, a University of Waterloo public health expert.

“The percentage of smokers in Canada and the U.S. has almost mirrored each other for much of the last 100 years.”

Hammond said the new study reflects earlier work that looked at populations of doctors and other health-care workers.

But he said the sheer numbers and broad population base of its subjects give it a heft and certainty those past papers lacked.

Smokers in both counties puff an average of 15 cigarettes a day. The study based its data on smokers who had quit for at least five years.