Several phenotypes, including height, BMI, HDL, TG, PC, and WBC (conditioned on ancestry at the Duffy antigen locus FY; see below), had h2 estimates lower than family-based estimates. This could be due to the phenotype-specific effects of epistasis, gene environment interaction, and/or shared environmental factors that can inflate family based estimates12,13. In our recent work using an extended genealogy inclusive of more distantly related individuals we also found height and BMI estimates lower than previous heritability estimates, providing further evidence of inflation11. The lower estimates could also reflect a difference in the heritability between African Americans and the previous study populations. There were no statistically significant differences in h2 estimates between the cohorts.
