Influence of Body Mass Index on the Age-related Slope of Total and Regional Bone Mineral Content

The influence of body mass index (BMI) on T scores for total body bone mineral content (TBBMC) and regional bone mineral content (RBMC) was studied in 186 healthy women: 100 postmenopausal, 35 perimenopausal, and 51 premenopausal. The three groups were divided by BMI >25 kg/m² and BMI <25 kg/m² and the postmenopausal women were further subdivided by years since menopause (YSM): <10, 10–20, and >20. Tartrate-resistant acid phosphatase (TRAP) concentration was higher in perimenopausal and postmenopausal women with BMI <25 kg/m² (P < 0.001). T scores for TBBMC and for axial or peripheral RBMC differed (P < 0.05 in all) between women with BMI >25 kg/m² and BMI <25 kg/m². The rate of perimenopausal and postmenopausal age-related slope of BMC, as reflected in all measurements, differed with BMI. In the overall group of women, the T score for TBBMC correlated significantly with BMI (r = 0.46, P < 0.0001); this correlation increased when adjusted for age (r = 0.62, P < 0.0001). BMI correlated with TRAP only in postmenopausal women (r = 0.57, P < 0.0001). Yearly TBBMC decline was twice as high in postmenopausal women with BMI <25 kg/m² (P= 0.0004) than in those with BMI >25 kg/m²; the decline of trunk RBMC was more significant (P < 0.0001). These findings confirm the influence of BMI and gonadal status on bone mass. Received 20 February 1996 / Accepted 31 December 1996