Table 1. Questionnaire items on smoking.

Study	Smoking status	Age at initiation	Current smoking	Age at cessation
GA2LEN	Have you ever smoked for as long as a year? ['YES' means at least one cigarette per day or one cigar per week for one year]	How old were you when you started smoking?	Have you smoked at all in the last month?	How old were you when you stopped smoking?
RHINE	Are you a smoker? (this applies even if you only smoke the odd cigarette/ cigar or pipe every week)		Are you an ex-smoker?	Stopped smoking in … (year)
ISAYA, ECRHS-Italy, GEIRD	Have you ever smoked for as long as a year? ['YES' means at least one cigarette per day or one cigar per week for one year]		Do you now smoke, as of one month ago?	How old were you when you stopped smoking?
ECRHS (clinical interview)	Have you ever smoked for as long as a year? ['YES' means at least 20 packs of cigarettes or 12 oz (360 grams) of tobacco in a lifetime, or at least one cigarette per day or one cigar per week for one year]		Do you now smoke, as of one month ago?	How old were you when you stopped or cut down smoking?*
ECRHS (postal questionnaire)	Have you ever smoked for as long as a year?		Have you smoked in the last month?	How old were you when you last smoked?

*only the answers from subjects who quit smoking were considered.