Effects of age and menopause on bone density of entire skeleton in healthy and osteoporotic women.

We studied 885 women to evaluate the effects of age and menopause on bone mineral density (BMD) in both healthy and postmenopausal osteoporotic subjects. The study cohort consisted of 161 healthy premenopausal women (age range 25-54 years), 357 healthy postmenopausal women (35-85 years) and 367 osteoporotic women (41-87 years). Total body and regional (spine, trunk, pelvis, arms, legs) BMD were measured with a dual-energy X-ray (DXA) device (Lunar DPX). Premenopausal BMD values remained essentially unchanged until the first half of the fourth decade, when they decreased. BMD values in both healthy postmenopausal and osteoporotic women were significantly lower than premenopausal values, and continued to decrease statistically after the onset of menopause. The highest Z-score (0.96 +/- 0.92) was found for total body BMD. Higher T-score values were found in osteoporotic than in normal postmenopausal women. In both healthy and osteoporotic postmenopausal women the best fits for BMD changes in total body, spine, trunk, arms and legs were obtained with the natural logarithm of years since menopause; only the pelvis BMD decreased linearly. Multiple regression analysis indicated that postmenopausal BMD changes in both normal and osteoporotic women were linked chiefly to body weight and years since the onset of menopause.