Secondary analyses using all 4 responses of time to first cigarette after waking (>60, 31–60, 6–30, ≤5 minutes) demonstrated a more robust effect of the metabolism metric in both COGA (p=0.03) and COGEND (p=0.004) as compared to the dichotomous time to first cigarette (>5 and ≤5 minutes) used in our primary analysis (Table S4 and Table 2, respectively). Figure S2 illustrates that across the 4 categories, there was an increased proportion of slow metabolizers at shorter times to first cigarette after waking among COGA daily smokers. In COGEND daily smokers, we observed a similar trend, except in the category of 31–60 minutes that only had 19 individuals (6% of sample, Table 1). Taken together, these results support a possible “dosage effect” where predicted slower metabolism was correlated with smoking sooner after waking.
