EDITOR—Studies investigating the impact on mortality of socioeconomic and lifestyle factors such as smoking tend to report death rates, death rate ratios, odds ratios, or the chances of smokers reaching different ages. These findings may also be converted into differences in life expectancy. We estimated how much life is lost in smoking one cigarette.

Our calculation is for men only and based on the difference in life expectancy between male smokers and non-smokers and an estimate of the total number of cigarettes a regular male smoker might consume in his lifetime. We derived the difference in life expectancy …