Smokers who quit by around age 40 can stave off an early death, according to a landmark study that fills key gaps in knowledge of smoking-related health ills.
While smokers who never stop lose about a decade of life expectancy, those who quit between ages 35 and 44 gained back nine of those years, the study found.
Moreover, the benefits of dropping the habit extend deep into middle age. Smokers who quit between 45 and 54 gained back six otherwise lost years, and those who quit between 55 and 64 gained four years.
Quitting young, before age 35, erased the entire decade of lost life expectancy.
The message: It's never too late to quit, even for heavy smokers with decades of puffing behind them.
But younger smokers should not be lulled into thinking they can smoke until 40 and then stop without consequences, said Prabhat Jha, an epidemiologist at the Center for Global Health Research in Toronto. Jha led the new study, published online Wednesday in the New England Journal of Medicine.
That's because the risks of lung cancer and other respiratory diseases linger for years after stubbing the last butt.
Most of the gains in life expectancy come because the twin risks of heart disease and stroke quickly drop after smoking ends. Both diseases occur as the byproducts of tobacco smoke trigger clotting in the arteries, a process that can rapidly reverse.
Damage to the lungs, meanwhile, takes longer to heal. "The risk for lung cancer doesn't disappear and the risk of respiratory disease doesn't disappear" in former smokers, said Jha. "But the acute risk for heart attack or stroke pretty much disappears."
While the study delivered some good news for quitters, it also hammered home the message that continuing to smoke carries grave risks.
Current smokers in the study died early at a rate triple that of people who never smoked. And few smokers reached age 80. Just 38 percent of female smokers and 26 percent of male smokers hit that milestone, while 70 percent of women who never smoked and 61 percent of men who never smoked did.