Longitudinal study on physical fitness parameters influencing bone mineral density reduction in middle-aged and elderly women: bone mineral density in the lumbar spine, femoral neck, and femur

The prolongation of the average life span of women has been associated with the rapidly aging society. However, serious problem have arisen as a result, such as an increase in the number of bed-ridden elderly patients with osteoporosis-associated femoral neck fracture. As preventive measures against osteoporosis for middle-aged to elderly women, 10,000 steps per day and intense exercise have been reported to inhibit bone mineral density (BMD) reduction. However, only a few studies have concretely reported on the type of physical fitness that is effective for BMD in particular parts of the body. In this study, a one-year longitudinal survey was performed involving generally healthy postmenopausal women to investigate physical fitness parameters influencing BMD in the lumbar spine, femoral neck, and femur. The subjects were 38 female residents of M City, aged 49-73 years. As physical fitness parameters, sit-ups, anteflexion in a sitting position, grip strength, mean amount of exercise (kcal), and area of outer body sway on standing straight with the eyes closed (m2) were measured. The BMD was measured in the lumbar spine (L2-L4), femoral neck, and femur. Logistic regression analysis was performed regarding the physical fitness parameters as explanatory variables and groups with and without BMD reduction over one year as those with and without risk as dependent variables. The number of sit-ups (odds ratio: 0.76, 95% CI: 0.61-0.96, p=0.022) was a preventive factor against BMD reduction of the lumbar spine, and ante flexion in a sitting position was a preventive factor against BMD reduction of the femoral neck (odds ratio: 0.88, 95% CI: 0.78-0.99, p=0.029). Regarding BMD reduction of the femur, the area of outer body sway on standing straight with the eyes closed tended to be not significant to the risk. It is suggested that physical fitness and local muscle strength are associated with BMD reduction in the lumbar spine, femoral neck, and femur.