Differences in bone mineral status between urban and rural Chinese men and women

Background: Few studies have investigated differences in bone health and associated lifestyle factors between urban and rural populations in countries, such as China, undergoing rapid nutrition transition. Such a study may help to identify risk factors of osteoporosis and provide evidence for future preventive strategies. Objective: To determine primarily whether differences in bone mineral content (BMC) and bone mineral density (BMD) exist between urban and rural Chinese men and women and secondly whether any urban-rural differences could be explained by body size or lifestyle factors. Methods: In total, 490 men and 689 women aged 50-70 were included in the study. 535 of them were from urban Shanghai and 644 from surrounding rural areas. Anthropometric measurements were conducted and spine lumber 1-4 BMC measurements were determined by dual-energy X-ray absorptiometry (DEXA). Information on socioeconomic status, medical history, smoking and drinking habits and physical activity were collected. Results: Urban men and women had significantly higher spine BMC, BMD and bone area than their rural counterparts (P < 0.01). After controlling body size, the differences between urban-rural spine BMC and BMD remained in women (P < 0.001), but were no longer significant in men. The urban and rural differences of BMC and BMD in women could not be explained by including the lifestyle factors such as income, intake of milk, vitamin D and calcium, total physical activity level, walking and social activity. Conclusion: This study found the significant differences in both spine BMC and BMD between urban and rural men and women in Shanghai, China. This difference could be explained by the body size in men; however, it remained unexplained in women after adjusting for body size and certain lifestyle risk factors.