Effect of urbanization on bone mineral density: A Thai epidemiological study

Background: The incidence of fractures in rural populations is lower than in urban populations, although the reason for this difference is unclear. This cross-sectional study was designed to examine the difference in bone mineral density (BMD), a primary predictor of fracture risk, between urban and rural Thai populations. Methods: Femoral neck and lumbar spine BMD was measured by dual-energy X-ray absorptiometry ( GE Lunar, Madison, WI) in 411 urban and 436 rural subjects ( 340 men and 507 women), aged between 20 and 84 years. Body mass index (BMI) was calculated from weight and height. Results: After adjusting for age and body weight in an analysis of covariance model, femoral neck BMD in rural men and women was significantly higher than those in urban men and women ( P < 0.001), but the difference was not observed at the lumbar spine. After stratifying by sex, age group, and BMI category, the urban-rural difference in femoral neck BMD became more pronounced in men and women aged < 50 years and with BMI greater than or equal to 25 kg/m(2). Conclusions: These data suggest that femoral neck BMD in rural men and women was higher than their counterparts in urban areas. This difference could potentially explain part of the urban-rural difference in fracture incidence.