Genetic influence on bone mineral density in Korean twins and families: the healthy twin study

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Bone mineral density (BMD), a representative marker of osteoporosis risk, is found to be highly heritable in this Korean study, which is very consistent with the findings in Western populations. This finding strongly supports that genetic factors are significant determinants of osteoporosis risk along with individual biological and behavioral factors. Although genetic factors are known to contribute significantly to variations in BMD in Western populations, such an association has not been fully evaluated in an Asian population. This study was conducted to determine the role of genetic factors on BMD in Korean population. The study participants were 2,728 men and women consisting of 497 monozygotic (MZ) twin pairs, 119 dizygotic (DZ) twin pairs, and 1,496 first-degree relatives from the Healthy Twin Study. BMD was measured using dual-energy X-ray absorptiometry. Quantitative genetic analysis based on a variance decomposition model was performed. Age and the measured covariates accounted for 17~61% of the variation in BMD, depending on the sites of measurement. After accounting for the covariate effects, the heritability of BMD at the whole body, thoracic and lumbar spine, whole ribs, whole pelvis, whole arms, and whole legs were 0.76, 0.72, 0.73, 0.71, 0.51, and 0.75, respectively. The pair-wise correlation of BMD was the highest within MZ twin pairs, followed by DZ twin pairs, sibling pairs, and parents-child pairs. Cross-trait correlation analysis revealed a positive genetic correlation between BMDs at different sites, ranging from 0.80 (arm and leg BMD) to 0.50 (pelvis and arm BMD). The high heritability of BMD in this Korean population similar to those found in Western populations and the significant common genetic basis between BMDs at different sites strongly supports a significant role of genetic determinants on the risk of osteoporosis.