Heritability of bone mineral density among Japanese women: A twin study

Background: Osteoporosis is a major risk factor for fractures among the older population. Despite osteoporosis being a significant concern in super-aged societies such as Japan, the heritability of bone mineral density within the Japanese populace remains unexplored. Therefore, we conducted a twin study among Japanese women to determine the extent of genetic and environmental influences on bone mineral density. Methods: The bone area ratio of 298 healthy, female Japanese twins (comprising 149 pairs, 136 monozygotic and 13 dizygotic twin pairs) registered in the Osaka University Twin Registry was measured using quantitative ultrasound. Classical twin analysis was employed to ascertain the heritability of bone mineral density. Results: The heritability of bone mineral density for the entire cohort was 0.51 (95 % confidence interval 0.38-0.63). For the women younger than 50 years, the effects of menopause were adjusted, and the best-fit model was also found to be the additive genetics and unique environment (AE) model, with a heritability estimate of 0.53 (95 % confidence interval 0.34-0.72). Conclusions: Compared with women from other countries, Japanese women appear to have a lower heritability of bone mineral density. Consequently, environmental factors may exert a larger influence on osteoporosis among Japanese women than among women of other races and ethnicities.