Analyses were conducted separately on the subset of genetically related individuals (227 families totaling 529 individuals). Single marker analyses were performed using PBAT (Lange et al, 2004). This statistical genetics program takes full advantage of the family structure, making use of both the between and within-family information (Fulker et al, 1999). All analyses were first conducted on the subset of “current frequent smokers” using the ethnic group information as covariates, and then conducted separately for the Caucasians. Three pairs of Monozygotic twins were removed and 10 suspected half siblings were removed from the data set prior to genetic analysis. Secondarily, because subject inclusion and recruitment criteria vary widely among genetic association studies, following the initial analysis, post hoc exploratory analyses were done to examine the effects of the inclusion criteria on the significance of the observed genetic associations. The inclusion criteria are described in Table 3.
