We analyzed the subjects with European ancestry with reported cigarettes per day (CPD) values included in the Nicotine Addiction Genetics (OZALC-NAG) study [28]; the Study of Addiction: Genetics and Environment (SAGE) [22]; and the Atherosclerosis Risk in Communities study (ARIC) [25], [26] (Table 1). Both the OZALC-NAG, which is an Australian family based study, and the SAGE study, which includes unrelated North American subjects, are GWAS ascertained based on substance dependence. In contrast ARIC is a population-based study designed to investigate the etiology of atherosclerosis in middle-aged adults [25]. Additional details for each of these studies is provided in Text S1 and elsewhere [28], [22] and [26].
