Association of body composition with predicted hip bone strength among Chinese postmenopausal women: a longitudinal study

Body composition and bone strength are closely associated. How lean mass (LM) and fat mass (FM) contribute to bone strength remains ambiguous. We investigated the associations of total body LM and FM with changes in predicted hip bone strength over a period of 3 years in 1,743 postmenopausal Chinese women from the communities of Guangzhou, China. The body compositions of the women were obtained with dual-energy X-ray absorptiometry. We used the hip structure analysis program to obtain the bone parameters at the femoral neck region, including the bone mineral density (BMD), cross-sectional area (CSA), cortical thickness (CT), section modulus (SM) and buckling ratio (BR). We found the FM and LM were positive predictors for hip bone strength (beta > 0, P < 0.05). The LM had a larger contribution to the BMD, CSA, CT, SM and/or their annual percent changes (vertical bar beta(LM)vertical bar > vertical bar beta(FM)vertical bar), while the contribution of FM to the BR and its annual percent change was higher than LM (vertical bar beta(FM)vertical bar > vertical bar beta(LM)vertical bar). Further analysis found that the associations of FM and LM with bone parameters were stronger in the underweight and normal weight participants (vertical bar beta(BMI1)vertical bar>vertical bar beta(BMI2)vertical bar). Overall, FM and LM had positive but differential effects on predicted hip bone strength, with a higher impact in the thinner participants.