Rural to urban migration is associated with adverse metabolic consequences, but its effect on osteoporosis risk is unclear. We investigated associations between rural to urban migration and bone mineral density (BMD) after accounting for changes in body composition. A cross sectional analysis was performed of ruralurban migrants (RUM) matched with rural non-migrated (RNM) siblings, plus a separate sample of urban-non-migrants (UNM). Participants (n=764, 54% male, mean age 49 years) were from the Indian Migration Study in Hyderabad. Lumbar spine (LS) and total hip (TH) BMD measured by DXA were the main outcomes. In minimally adjusted models, rural to urban migration was associated with a higher BMD in females; TH BMD: 0.928 (0.014), 0.899 (0.009) and 0.870 (0.012) g/cm2 (P=0.002); LS BMD: 0.923 (0.015), 0.904 (0.010) and 0.855 (0.014) g/cm2 (P=0.06) (mean (S.E.M.), UNM, RUM and RNM, respectively). Conversely, no difference was seen in males (P<0.001 for gender interaction). In regression analyses fat mass, lean mass and insulin were related to BMD, but lean mass was the only independent predictor. In further comparisons of BMD according to migration status, adjusting for lean mass; rural to urban migration was no longer related to BMD in females, whereas a decrease in BMD was seen in males with migration; TH BMD: 0.883 (0.011), 0.904 (0.007) and 0.924 (0.009) g/cm2 (P=0.005); LS BMD: 0.863 (0.015), 0.891 (0.009) and 0.918 (0.012) g/cm2 (P=0.003) (adjusted BMD in males, UNM, RUM and RNM, respectively). In summary rural to urban migration was associated with a higher BMD in females whereas no difference was seen in males. After adjusting for differences in lean mass, no association was evident between urban migration and BMD in females, whereas a negative association was observed in males. Hence, rural to urban migration may represent a risk factor for osteoporotic fracture in males.
18 - 21 May 2013
European Calcified Tissue Society