Pack year for cigarette smoking as a risk factor

Pack year for cigarette smoking as a risk factor

Number of cigarettes in a pack is taken as twenty. If a person has been smoking one pack per year for five years, it is taken as five pack years. If it was forty cigarettes per day for three years, it will be taken as six pack years. In short, pack year for cigarette smoking as a risk factor is the number of packs smoked per day multiplied by the number of years the person has been a smoker.