Bone Mineral Density Changes During the Menopause Transition in a Multiethnic Cohort of Women

Abstract

Bone loss accelerates after menstruation ends, but it is not clear when bone loss begins or at what rate bone is lost at various stages of the transition to menopause. Such knowledge would help to determine when to screen for osteoporosis and when to consider treatment. The SWAN (Study of Women’s Health Across the Nation), a longitudinal multiethnic cohort study of menopausal transition, provided an opportunity to track bone mineral density (BMD) at the lumbar spine and proximal femur in 1902 African American, Caucasian, Chinese, and Japanese women who, at baseline, were premenopausal or at the early perimenopausal stage and ranged in age from 42 to 52 years. The women were evaluated at up to 6 annual visits. When menopausal stage was estimated from the frequency and regularity of menstrual bleeding, little change in BMD was noted in the premenopausal or early perimenopausal stages. During late perimenopause, however, with no menstrual bleeding in the past 3 months but some bleeding in the past 11 months, BMD declined substantially. Equal or greater rates of bone loss from the spine and hip were documented in postmenopausal women who had been amenorrheic for at least 12 consecutive months. In both the late perimenopausal and postmenopausal phases, bone loss was about 35–55% slower in women in the top tertile of body weight than in those in the bottom tertile. Ethnic differences in rates of spinal bone loss were predominantly explained by differences in body weight. These findings suggest that screening for osteoporosis should be considered in women who have entered late stages of the menopausal transition—particularly those whose body weight is relatively low.