Association between obesity and bone mineral density in middle-aged adults

Background The relationship between obesity and bone mineral density (BMD) varies in different studies. Our aim in this study was to explore the association between obesity (body mass index >= 30) and BMD among adults 40-59 years of age. Methods This study was conducted on a sample of 2218 participants (986 men and 1232 women) aged 40 to 59 years from the National Health and Nutrition Examination Survey 2011-2018. The independent variable was body mass index (BMI). The outcome variable was lumbar BMD. The associations of BMI with lumbar BMD were examined using multivariable linear regression models. Results BMI was positively associated with lumbar BMD after adjusting for other covariates [beta 0.006; 95% confidence interval (CI) 0.003-0.008]. An inverted U-shaped association between BMI and lumbar BMD was further identified, with the point of infection at approximately 50 kg/m(2). In the subgroup analyses, the relationship between BMI and lumbar BMD in women and blacks was an inverted U-shape. Conclusion Based on the results, it may be beneficial to appropriately increase BMI to promote BMD. However, considering the inverted U-shaped association, excessive BMI may be harmful to bone health in women and blacks.