456 Race and leukocyte telomere length, S. C. Hunt et al. Statistical analyses The primary analysis consisted of comparing LTL parameters between African Americans and whites, and between men and women after adjustment for age and BMI. To investigate cross- sectional, race-specific associations of age with LTL, sex- and BMI-adjusted LTLs from each study were combined and analyzed by generalized estimating equations and an exchangeable correlation matrix (PROC GENMOD in SAS) to correct the estimated standard errors for the relatedness of the subjects within families. This correction prevents inflated significance levels of the tests used in the analyses presented. An age-by-race interaction term was included in the model to test if there were different age-related cross-sectional rates of LTL shortening between the two races. When significant, this interaction term was replaced by nesting age within race to estimate the two different slopes and their standard errors. Sex-by-age interactions with LTL shortening were not significant. Race-specific heritabilities of LTL in the FHS were obtained from SOLAR (Almasy & Blangero, 1998), adjusting for sex, age and specific gel on which the sam- ple was run. Unless otherwise indicated, data are presented as mean ± SEM. Acknowledgments This study was supported by National Institutes of Health grants AG16592, AG020132, HL38844, U01 HL 67893, U01 HL67894, U01 HL67895, U01 HL67896, U01 HL67897, U01 HL67898, U01 HL67899, U01 HL67900, U01 HL67901, and U01 HL67902 and the HealthCare Foundation of New Jersey. References Aiyer AN, Kip KE, Marroquin OC, Mulukutla SR, Edmundowicz D, Reis SE (2007) Racial differences in coronary artery calcification are not attributed to differences in lipoprotein particle sizes: the heart strategies concentrating on risk evaluation (Heart SCORE) Study. Am. Heart J. 153, 328–324. Akkad A, Hastings R, Konje JC, Bell SC, Thurston H, Williams B (2006) Telomere length in small-for-gestational-age babies. BJOG. 113, 318– 323. Allshire RC, Dempster M, Hastie ND (1989) Human telomeres contain at least three types of G-rich repeat distributed non-randomly. Nucleic Acids Res. 17, 4611–4627. Almasy L, Blangero J (1998) Multipoint quantitative-trait linkage analysis in general pedigrees. Am. J. Hum. Genet. 62, 1198–1211. Andrew T, Aviv A, Falchi M, Gardner JP, Lu X, Kimura M, Kato BS, Valdes AM, Spector TD (2006) Mapping genetic loci that determine leukocyte telomere length in a large sample of unselected, female sibling-pairs. Am. J. Hum. Genet. 78, 480–486. Athens JW, Raab SO, Haaab OP, Mauer AM, Ashenbrucker H, Cartwright GE, Wintrobe MM (1961) Leukokinetic studies. III. The distribution of granulocytes in the blood of normal subjects. J. Clin. Invest. 40, 159– 164. Aviv A, Valdes A, Gardner JP, Swaminathan R, Kimura M, Spector TD (2006a) Menopause modifies the association of leukocyte telomere length with insulin resistance and inflammation. J. Clin. Endocrinol. Metab. 91, 635–640. Aviv A, Valdes AM, Spector TD (2006b) Human telomere biology: Pitfalls of moving from the laboratory to epidemiology. Int. J. Epidemiol. 35, 1424–1429. Bain BJ, Phillips D, Thomson K, Richardson D, Gabriel I (2000) Investigation of the effect of marathon running on leucocyte counts of subjects of different ethnic origins: relevance to the aetiology of ethnic neutropenia. Br. J. Haemotol. 108, 483–487. Baird DM, Britt-Compton B, Rowson J, Amso NN, Gregory L, Kipling D (2006) Telomere instability in the male germline. Hum. Mol. Genet. 15, 45–51. Bakaysa SL, Mucci LA, Slagboom PE, Boomsma DI, McClearn GE, Johansson B, Pedersen NL (2007) Telomere length predicts survival independent of genetic influences. Aging Cell 6, 769–774. Balaban RS, Nemoto S, Finkel T (2005) Mitochondria, oxidants, and aging. Cell 20, 483–495. Bekaert S, De Meyer T, Rietzschel ER, De Buyzere ML, De Bacquer D, Langlois M, Segers P, Cooman L, Van Damme P, Cassiman P, Van Criekinge WV, Verdonck P, De Backer GG, Gillebert TC, Van Oostveldt P, on behalf of the Asklepios investigators (2007) Telomere length and cardiovascular risk factors in middle-aged population free of overt cardiovascular disease. Aging Cell 6, 639–647. Benetos A, Gardner JP, Zureik M, Labat C, Xiaobin L, Adamopoulos C, Temmar M, Bean KE, Thomas F, Aviv A (2004) Short telomeres are associated with increased carotid atherosclerosis in hypertensive subjects. Hypertension 43, 182–185. Benetos A, Okuda K, Lajemi M, Kimura M, Thomas F, Skurnick J, Labat C, Bean K, Aviv A (2001) Telomere length as indicator of biological aging: the gender effect and relation with pulse pressure and pulse wave velocity. Hypertension 37 (2), 381–385. Bischoff C, Petersen HC, Graakjaer J, Andersen-Ranberg K, Vaupel JW, Bohr VA, Kølvraa S, Christensen K (2006) No association between telomere length and survival among the elderly and oldest old. Epidemiology 17, 190–194. Brouilette SW, Moore JS, McMahon AD, Thompson JR, Ford I, Shepherd J, Packard CJ, Samani NJ, West of Scotland Coronary Prevention Study Group (2007) Telomere length, risk of coronary heart disease, and statin treatment in the West of Scotland Primary Prevention Study: a nested case-control study. Lancet 369 (9556), 107–114. Brouilette S, Singh RK, Thompson JR, Goodall AH, Samani NJ (2003) White cell telomere length and risk of premature myocardial infarction. Arterioscler. Throm. Vasc. Biol. 23, 842–846. op den Buijs J, van den Bosch PPJ, Musters MW, van Riel (2004) Mathematical modeling confirms the length-dependency of telomere shortening. Mech. Ageing Dev. 125, 437–444. Butler MG, Tilburt J, DeVries A, Muralidhar B, Aue G, Hedges L, Atkinson J, Schwartz H (1998) Comparison of chromosome telomere integrity in multiple tissues from subjects at different ages. Cancer Genet. Cytogenet. 105, 138–144. Cawthon RM (2002) Telomere measurement by quantitative PCR. Nucleic Acids Res. 30: e47. Cawthon RM, Smith KR, O’Brien E, Sivatchenko A, Kerber RA (2003) Association between telomere length in blood and mortality in people aged 60 years or older. Lancet 361, 393–395. Cherkas LF, Aviv A, Valdes AM, Hunkin JL, Gardner JP, Surdulescu GL, Kimura M, Spector TD (2006) The effects of social status on biological ageing as measured by white-blood-cell telomere length. Aging Cell 5, 361–365. Coale AJ, Kisker EE (1986) Mortality crossovers: reality or bad data? Population Studies 40, 1. Corti MC, Guralink JM, Ferruci L, Izmirlian G, Leveille SG, Pahor M, Cohen HJ, Pieper C, Havlik HJ (1999) Evidence for black-white crossover in all-cause and coronary artery disease mortality in an older popula- tion. The North Carolina EPESE. Am. J. Public Health 89, 308–314. © 2008 The Authors Journal compilation © Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland 2008