We selected four continuous and three binary smoking behaviors for analysis (Table 1). The continuous measures were cigarettes smoked per day (CPD), age at smoking initiation (SMKAGE), duration of smoking (SMKDU) and pack-years (PKYRS); the binary measures were ever versus never smoking status (EVNV), smokers who quit versus those who did not (CIGSTAT), and a binary measure of smoking intensity (CPDBI, defined as ten or more cigarettes per day versus fewer than ten). Only current or former smokers were included in the analyses involving the smoking phenotypes with the exception of EVNV which included never smokers.
