The participants were 1366 individuals from 402 AA families and 671 individuals from 200 EA families. The average age was 39.4 ± 14.4 (SD) years for the AA and 40.5 ± 15.5 years for the EA participants. The average nuclear family size was 3.14 ± 0.75 for AAs and 3.17 ± 0.69 for EAs. There were 1053 and 515 smokers in the AA and EA, samples, respectively, whereas all the rest had smoked fewer than 100 cigarettes in their lifetimes. The average HSI and FTND scores for smokers were 3.7 ± 1.4 and 6.26 ± 2.15, respectively for AAs and 3.9 ± 1.4 and 6.33 ± 2.22 for EAs. Age of smoking onset was 17.3 ± 4.7 (mean ± SD; years) and 15.5 ± 4.4, for the AA and EA samples, respectively. Years smoked were 20.4 ± 12.5 (mean ± SD) and 23.2 ± 13.5 for the AA and EA samples, respectively. The average number of cigarettes smoked per day was 19.4 ± 13.3 for AA smokers and 19.5 ± 13.4 for EA smokers. Detailed demographic and clinical characteristics of the two samples have been reported elsewhere (Li and others 2005; Li and others 2008b; Li and others 2006)
