Effects of bone mineral density of the lumbar spine and prevalent vertebral fractures on the risk of immobility
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To clarify the contribution of osteoporosis to future immobilization, a prospective observational study was carried out on Japanese postmenopausal women. The prevalence of low bone mineral density (BMD) and vertebral fracture were independent risks for future immobilization.
Immobilization by hip fracture requires more medical care and higher costs. Osteoporosis increases the risk of hip fracture, but there is little data linking osteoporosis and immobilization in postmenopausal Japanese women.
The study participants consisted of postmenopausal ambulatory volunteers. Baseline information such as BMD, prevalent fractures, comorbidities, pain in the body, and variables were obtained from 1993, and time course of occurrence of immobilization was observed until 2008.
A total of 1,312 participants were enrolled and were observed for a total of 6.7 ± 4.1 years. A total of 75 subjects suffered immobilization. In multivariate analysis to calculate the Cox’s hazard ratio of baseline parameters for immobilization, four independent variables were observed: age (hazard ratio, 1.52 [95% CI, 1.29 to 1.80], p = 0.000), pain in the body (2.54 [1.42 to 4.89, p = 0.001]), low BMD (1.83 [1.10 to 3.13, p = 0.020]), and dementia (3.58 [91.80 to 6.76, p = 0.001]). The hazard ratio of prevalent vertebral fracture was 1.98 (1.20 to 3.30, p = 0.007) instead of low BMD of above model.
These results indicate that low BMD and prevalent vertebral fracture pose an independent risk for future immobilization in postmenopausal Japanese women.