This study, conducted by Richard Doll, Richard Peto, Jillian Boreham, and Isabelle Sutherland, aimed to compare the hazards of cigarette smoking in men who formed their habits at different periods and the extent of the reduction in risk when cigarette smoking is stopped at different ages. The study, which began in 1951 and continued until 2001, involved 34,439 male British doctors. The results showed that men born in the 1920s who smoked cigarettes and continued to do so died about 10 years younger than lifelong non-smokers. Cessation at age 60, 50, 40, or 30 years gained, respectively, about 3, 6, 9, or 10 years of life expectancy. The excess mortality associated with cigarette smoking was less for men born in the 19th century and was greatest for those born in the 1920s. The study concluded that the substantial progressive decrease in mortality rates among non-smokers over the past half century has been outweighed by a progressive increase in the smoker versus non-smoker death rate ratio due to earlier and more intensive use of cigarettes. Among men born around 1920, prolonged cigarette smoking from early adulthood tripled age-specific mortality rates, but cessation at age 50 halved the hazard, and cessation at age 30 avoided almost all of it.This study, conducted by Richard Doll, Richard Peto, Jillian Boreham, and Isabelle Sutherland, aimed to compare the hazards of cigarette smoking in men who formed their habits at different periods and the extent of the reduction in risk when cigarette smoking is stopped at different ages. The study, which began in 1951 and continued until 2001, involved 34,439 male British doctors. The results showed that men born in the 1920s who smoked cigarettes and continued to do so died about 10 years younger than lifelong non-smokers. Cessation at age 60, 50, 40, or 30 years gained, respectively, about 3, 6, 9, or 10 years of life expectancy. The excess mortality associated with cigarette smoking was less for men born in the 19th century and was greatest for those born in the 1920s. The study concluded that the substantial progressive decrease in mortality rates among non-smokers over the past half century has been outweighed by a progressive increase in the smoker versus non-smoker death rate ratio due to earlier and more intensive use of cigarettes. Among men born around 1920, prolonged cigarette smoking from early adulthood tripled age-specific mortality rates, but cessation at age 50 halved the hazard, and cessation at age 30 avoided almost all of it.