dichotomized FTND variable were tested by age of onset condition within each cohort separately (Table 4). There was a significant HA vs. HC contrast in the early onset group for each cohort (P's = 0.02−0.001, OR's = 1.5–3.0), but this contrast was not significant in any cohort in the late onset condition. Thus, the relative risk/protective effect of haplotypes A and C was found only in early onset smokers in three separate cohorts.
