EPIC cohort. Study participants were classified as never, current or ex-smokers. Duration of smoking was calculated based on collected information on age of smoking initiation and age at recruitment for current smokers or age at smoking cessation for ex-smokers. Additionally, information on the number of cigarettes currently smoked and smoked at ages 20, 30, 40, and 50 was collected. Based on this information, the average number of cigarettes per day (CPD) was calculated. Information on smoking interruptions was available only for four coordinating centres in EPIC and therefore not taken into account.
