Contributions of chronological age, age at menarche and menopause and of anthropometric parameters to axial and peripheral bone densities.

Bone mineral density (BMD) was measured in 128 normal postmenopausal women at different skeletal sites: lumbar spine and proximal femur, using dual-energy X-ray absorptiometry (DXA), and the cancellous and cortical envelopes of the distal third of radius and tibia, using precise low-dose quantitative computed tomography (QCT). Multivariate analysis included chronological age, ages related to menstrual history (menopause and menarche) and anthropometric factors, e.g. height and weight, as independent predictive variables. Weight is a much-studied predictor of bone density. At sites of high bone turnover, i.e. cancellous envelope, the effect of weight appeared overshadowed by estrogen-related parameters: age-past-menopause was the first predictor of BMD in the cancellous compartment of radius and in Ward's triangle, and the number of reproductive years was the strongest predictor of BMD in the cancellous compartment of tibia and in the spine (L2-4). This suggests that in addition to menopause, the length of menstrual life should be considered as an explanation for the variations in current bone mass in postmenopausal women. At the cortical level of radius, the effect of chronological age was predominant. At the cortical level of tibia, height and weight were the best predictors of BMD. We conclude that the influence of parameters related to menstrual history is predominant in sites with mainly cancellous tissue and that anthropometric factors constitute the best predictors of BMD in the cortical sites of weight-bearing bones.