For Cohort I, history of regular smoking was assessed only in the 1988–89 questionnaire. Respondents who self-described as “ex-” or “current smoker”(s) were coded positive for regular smoking in Cohort I. For Cohort II, regular smoking was coded if respondents reported i) having smoked 100 or more cigarettes, or ii) smoking less than 100, but more than 20 cigarettes, and having smoked at least one or two days per week for a period of three weeks or more. For Cohort II, age of onset of regular smoking was defined as age first smoked at least one or two days per week for a period of three weeks or more. Age of onset of regular smoking was not assessed in Cohort I.
