452 Race and leukocyte telomere length, S. C. Hunt et al. Table 1 Means (± standard deviation) of age and body mass index of the two cohorts Whites Men (n = 610) 57.3 ± 13.6 29.4 ± 4.7 (n = 140) 30.9 ± 4.6 27.8 ± 5.3 Whites Men 6.67 ± 0.03 6.68 ± 0.03 6.68 ± 0.03 7.28 ± 0.06 7.29 ± 0.06 7.30 ± 0.06 Women (n = 785) 58.5 ± 13.1 28.4 ± 5.9 (n = 207) 30.1 ± 4.8 25.5 ± 6.1 Women 6.77 ± 0.03 6.81 ± 0.03 6.80 ± 0.03 7.32 ± 0.05 7.31 ± 0.05 7.29 ± 0.05 FHS Age (years) Body mass index (kg m–2) BHS Age (years) Body mass index (kg m–2) BHS, Bogalusa Heart Study; FHS, Family Heart Study. FHS LTL Age-adjusted LTL Age- and BMI-adjusted LTL BHS LTL Age-adjusted LTL Age- and BMI-adjusted LTL BMI, body mass index; BHS, Bogalusa Heart Study; FHS, Family Heart Study. African Americans Men (n = 195) 52.4 ± 10.6 30.6 ± 6.1 (n = 44) 31.6 ± 3.9 28.6 ± 8.2 Women (n = 378) 54.0 ± 10.9 34.1 ± 7.8 (n = 94) 29.4 ± 5.0 30.6 ± 8.6 Entire sample Men (n = 805) 56.1 ± 13.1 29.7 ± 5.1 (n = 184) 31.1 ± 4.4 28.0 ± 6.1 African Americans Men 6.93 ± 0.05 6.86 ± 0.05 6.86 ± 0.04 7.81 ± 0.10 7.83 ± 0.11 7.84 ± 0.11 Women 7.16 ± 0.04 7.10 ± 0.03 7.12 ± 0.04 7.95 ± 0.08 7.93 ± 0.08 7.97 ± 0.08 Women (n = 1163) 57.1 ± 12.6 30.2 ± 7.1 (n = 301) 30.0 ± 4.9 27.1 ± 7.4 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 p gender p race < 0.0001 < 0.0001 < 0.0001 0.5087 0.5241 0.2590 Table 2 Leukocyte telomere parameters by race and sex in the two cohorts, in which leukocyte telomere length (LTL) was measured using restriction enzymes HinfI/RsaI Fig. 1 Age- and body mass index-adjusted leukocyte telomere length (LTL) in the NHLBI Family Heart Study (FHS) and the Bogalusa Heart Study (BHS), based on terminal restriction fragment lengths, determined in the entire sample by HinfI/ RsaI restriction enzymes. The lower LTL values in the FHS than the BHS cohorts relate to the older age of the participants of the FHS. artery calcification than do whites (Tang et al., 1995; Yan et al., 2006; McClelland et al., 2006; Aiyer et al., 2007; Loria et al., 2007). We therefore explored in two ongoing studies, the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study (FHS) and the Bogalusa Heart Study (BHS), the racial effect on LTL. Results Mean ages and BMI of whites and African Americans, by sex, are displayed in Table 1. In both the FHS and the BHS cohorts, LTL, measured by Southern blots of the terminal restriction fragment (TRF) products of HinfI/RsaI, was significantly longer in African Americans than in whites (Table 2; Fig. 1). As LTL was inversely correlated to BMI (r = –0.071, p = 0.002), we adjusted LTL for the BMI. For the FHS cohort, sex-specific differences in age- and BMI-adjusted LTL between African Americans and whites were 180 base pairs (bp) for men and 320 bp for women; for the BHS cohort, these differences amounted to 500 bp for men and 680 bp for women. Heritability of LTL in whites was 0.69 ± 0.03, while in African Americans it was 0.78 ± 0.09, both significant at p < 0.0001. There was no statistically significant difference in heritability between African Americans and whites. In the FHS cohort, women of both races displayed significantly longer LTL than men (Table 2; Fig. 1). The sex-related differences in age- and BMI-adjusted LTL for this cohort were 120 bp for © 2008 The Authors Journal compilation © Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland 2008