The association between abdominal obesity and femoral neck bone mineral density in older adults

BACKGROUND: The relationship between obesity and osteoporosis is complex, with contradictory findings reported. Our aim was to evaluate the association between waist circumference (WC), as an easy-to-determine clinical index of abdominal obesity, and femoral neck bone mineral density (BMD) among older adults, using the National Health and Nutrition Examination Survey (NHANES) database. METHODS: Data of five NHANES cycles (2005–2010, 2013–2014, and 2017–2018), including 5801 adults aged ≥ 60 years, were used in the analysis. Weighted multiple regression analyses were performed to evaluate the association between WC and femoral neck BMD. Weighted generalized additive models and smooth curve fitting were further performed to characterize nonlinearities in the association. RESULTS: There was a positive association between WC and femoral neck BMD in non-adjusted models. After adjusting for body mass index (BMI), the association became negative. On subgroup analysis stratified by sex, this negative association only existed for men. An inverted U-shaped curve relationship between WC and femoral neck BMD was further identified, with an inflection point at a WC of 95 cm for both men and women. CONCLUSIONS: Abdominal obesity is a negative predictor of bone health among older adults, independent of BMI. The association between WC and femoral neck BMD followed an inverted U-shaped curve.