Nearly 300,000 people (age range, 59–82) completed questionnaires about their medical history and their smoking behaviors during nine periods in their lives, beginning with before their 15th birthday until after age 70 (for older participants).
Those who reported smoking less than a cigarette a day, on average, over their lifetimes were 64 percent more likely to die prematurely from any cause than those who never smoked—chiefly from lung cancer, but also due to other respiratory diseases and cardiovascular disease. Among people who smoked one to 10 cigarettes a day, the risk of dying prematurely from any cause was 87 percent higher than that of respondents who never smoked.
When researchers looked at specific causes of death, they found that those who smoked less than one cigarette per day over their lifetimes had nine times the risk of dying from lung cancer compared with never smokers. Those who smoked between one and 10 cigarettes had 12 times the risk.
Importantly, the study also found that quitting smoking, even for light smokers, significantly reduces the chance of death from smoking-related causes—and the younger you are when you quit, the greater the reduction in risk.