Patterns and predictors of bone mineral density and its change among pre-, and early postmenopausal women: Toward the identification of at-risk women.

Abstract

Osteoporosis is a potentially debilitating, chronic condition, whose sequelae, fractures, are likely to garner increasing medical and public health resources as our population ages. Developing effective prevention strategies may depend on understanding factors associated with the achievement of optimal bone mineralization as well as the determinants of bone loss. Among women, declining ovarian function around the time of menopause, delineates a period of increasing risk for lower bone mineral density (BMD), the precursor to osteoporosis. The menopausal transition offers an important time to evaluate the characteristics that may affect this risk for lower BMD. A longitudinal analysis of six year's of data from the Michigan Bone Health Study, a prospective cohort study of 614 women, aged 24--44 at baseline, provided insight into the natural history of bone loss, risk factors associated with BMD status, and risk factors associated with BMD loss. Rates of BMD change for pre-, peri-, and postmenopausal women were estimated and compared, with up to five BMD measurements at the lumbar spine and the femoral neck. BMD measured at the lumbar spine was curvilinear with respect to time, while BMD measured at the femoral neck was linear and began as early as 24 years of age. Rates of bone loss were not significantly associated with age in this group of pre-and-peri-menopausal women. Important and independent predictors of pre- and perimenopausal BMD status were body weight, family history of osteoporosis, fracture history, past physical activity, and modest alcohol consumption. Reaching postmenopausal status and reporting a history of breast, ovarian or uterine cancer were strongly related to increased rate of BMD loss. Greater body weight was protective for BMD loss. Baseline osteocalcin (OCN), a bone matrix protein found in serum that indicates bone turnover, was not predictive of subsequent BMD after controlling for baseline BMD. Only the repeated annual measures of OCN were independently associated with BMD, with the only sizeable effect among postmenopausal women. Understanding the distinction between factors related to BMD status and those related to BMD loss might help women to adopt healthy personal practices and health planners to develop programs that curtail an increasing trend in osteoporotic fracture.