Cigarette smoking is the primary cause of lung cancer throughout the world.

The risk of developing lung cancer is related to the total dose of smoke to which you have been exposed during your lifetime. This can be estimated in several ways including: the number of cigarettes smoked per day, the depth of smoke inhalation, the number of pack-years, and the age at which smoking began.

These measures of exposure correlate well with the risk of getting lung cancer, but they are subjective measures and rely on the truthfulness and accuracy of the information smokers report about themselves. Recently, a novel method of more accurately determining smoke cumulative smoke exposure was reported in the American Journal of Epidemiology.