Familial aggregation of central obesity in Southern Indians

BACKGROUND: High prevalence of diabetes in South Asians is associated with a pronounced tendency to abdominal obesity. This intermediate quantitative trait may be more amenable than type 2 diabetes to genetic linkage studies. OBJECTIVES: To derive a measure of central obesity independent of total adiposity and adjusted for factors under environmental influence, and to estimate the genetic contribution to familial aggregation of this trait. SUBJECTS AND METHODS: A total of 1295 individuals from 300 families were studied in a community-based cross-sectional study in Chennai, India. Central fat was measured using sagittal abdominal diameter, and adjusted for age, BMI and body fat percentage measured by impedance. Intra-sibship correlations were calculated for adjusted sagittal abdominal diameter and a comparison variable, adjusted body fat percentage. RESULTS: Among individuals free of diabetes, intra-sibship correlations were 0.48 for adjusted sagittal abdominal diameter and 0.14 for adjusted body fat percentage. CONCLUSIONS: Even after adjustment for possible assortative mating, these results are consistent with a heritability exceeding 90% for a trait defined as abdominal fat accumulation adjusted for total adiposity, sex and age. Linkage studies of abdominal obesity that map one or more of the genes underlying this high heritability are therefore a possible route to identifying genes for type 2 diabetes in South Asians.