Risk Factors for Low Bone Mineral Density among Females: The Effect of Lean Body Mass

Background.This study determines if body composition and lifestyle are risk factors for low radius-bone mineral density (R-BMD) and evaluates the role of body composition in the age-related decline of R-BMD. Methods.Data on age, menopausal status, fat mass, lean body mass (LBM), drinking, smoking, and occupation were collected from 3,867 females ages 37–69, whose R-BMD was also measured. Multiple logistic regression analyses examined the predictive accuracy of these factors for low (20th percentile) R-BMD. Results.Age, LBM, and menopausal status were risk factors for the 37–55 age group, while age, LBM, and lifestyle (alcohol consumption 3 or fewer days per week and currently smoking) were risk factors for the 56–69 age group. The odds ratio (OR) for LBM was nearly reciprocal to the ORs for age and for menopausal status. Our model has low sensitivity, high specificity, low positive predictive value, and high negative predictive value. Conclusions.Consumption of alcohol 3 or fewer days per week and being a current smoker have a negative effect on R-BMD among older (56–69) women. The positive effect of LBM on R-BMD continues from age 37 on. LBM has an effect almost equal but opposite to those of aging and menopause on the risk of low R-BMD. High LBM after age 37 predicts normal R-BMD.