Birth weight as a predictor of adult bone mass in postmenopausal women: The Rancho Bernardo study

Understanding the determinants of adult bone mass may help to identify wome n for prevention of osteoporosis. We postulated that birth weight would pre dict low adult bone mass in old age. Subjects were 305 postmenopausal Cauca sian women (mean age 70 years). Bone mineral content (BMC) and bone mineral density (BMD) were measured at the wrist, forearm, hip and lumbar spine. B irth weight was assessed by self-report. Birth weight was positively con-el ated with BMC at the forearm (r = 0.15), hip (r = 0.12) and lumbar spine (r = 0.18). and the age-adjusted mean BMC increased significantly from the lo west to the highest birth weight tertile. Adjusting for adult weight dimini shed this association at the forearm and hip, but not at the spine. Adjustm ent for multiple other covariates, including height, did not materially cha nge these associations. Adult weight and height were significantly con-elat ed with birth weight (r = 0.19 and r = 0.24, respectively). Birth weight wa s not independently correlated with BMD. Birth weight was thus positively c orrelated with adult weight and BMC 70 years later. These findings suggest that low birth weight may be a marker for future low bone mass and that dif ferent mechanisms exist for establishing the adult bone envelope (estimated by BMC) versus its density (estimated by BMD).