By this point, everyone is aware that not smoking -- or at the very least, giving it up -- is good for your health. But a new study of more than a million women shows just how much longer you'll live by giving up the habit.
The study, published in The Lancet, shows that stopping smoking may help women live a decade longer than they would have if they had continued lighting up.
Researchers also found that the more the women smoked, the higher their risk of premature death, with even "light" smokers (those who smoked just one to nine cigarettes a day) having a doubled risk of death compared with non-smokers.
"If women smoke like men, they die like men -- but, whether they are men or women, smokers who stop before reaching middle age will on average gain about an extra ten years of life," study researcher Professor Sir Richard Peto, of the University of Oxford, said in a statement.
The study included 1.3 million women who joined the Million Women Study between 1996 and 2001 when they were between the ages of 50 and 65. Researchers surveyed them on their health habits and found that 20 percent of them smoked, 28 percent used to smoke and 52 percent never smoked. The researchers then re-surveyed them three years later to check on their smoking statuses.
The women were then followed for another nine years, on average, at which point about 66,000 of them had died.
The researchers found that those who still smoked at the three-year re-survey point were almost three times more likely to die by the end of the whole study period, compared with the never-smokers.
The researchers also found that the deaths between smokers and non-smokers differed in that the smokers were more likely to die from diseases like stroke, lung disease or cancer, or heart disease.
Taking into account the nearly three-fold death risk smokers have compared with non-smokers, researchers extrapolated that smoking causes two out of three deaths among smokers in their 50s, 60s and 70s.
Researchers also investigated how much lower of a death risk a person had if they quit smoking by a certain age. They found that women who stopped smoking by age 30 were able to lower their risk of dying early 97 percent, while those who stopped before age 40 lowered their early death risk 90 percent.
They also found that people who didn't stop smoking until age 40 experienced negative health effects for decades after stopping, but these effects are 10 times worse for people who keep smoking post-40.