Perimenopause, the transition into menopause, marks the beginning of accelerated bone loss, contributing to the development of osteoporosis, a major public health problem. This perimenopausal transition has also been associated with a decrease in body lean mass, an increase in fat mass, and an increase in body weight. How these changes in fat mass and lean mass may influence bone mineral density (BMD) is currently unknown. The purpose of this study is to determine the independent effect and relative contribution of lean mass and fat mass to BMD in perimenopausal women.
The sample consisted of 43 sedentary perimenopausal women (age: mean = 49.6; S.D. = 3.2) with an intact uterus and ovaries, participating in a study of exercise and perimenopausal symptoms. Total body BMD, regional BMD, and soft tissue body composition were measured by dual-energy X-ray absorptiometry. Other measures including age, height, weight, and serum FSH and E2 were also obtained.
Findings revealed that 14% of these perimenopausal women had low bone mass (osteopenia) in the lumbar spine and/or the femoral neck. Overall body fat mass and lean mass had positive relationships with BMD of lumber spine and the femur. However, using multiple regression analyses, only lean mass and ethnicity remained significant predictors for BMD of the femoral neck (r2 = 45%) with lean mass explaining more variance than ethnicity. Lean mass was the sole predictor of total proximal femur BMD explaining 38% of the variance. Fat mass was not a significant predictor of BMD at any skeleton site.
These findings suggest that body lean mass, not fat mass, is a significant contributor to femoral BMD in perimenopausal women.