Risk factors of osteoporosis in healthy elderly with unrecognized obstructive sleep apnea: role of physical activity.

OBJECTIVE: Several studies suggest a relationship between bone mineral density (BMD) anthropometric and metabolic variables, and obstructive sleep apnea (OSA); all of these factors have an effect on osteoporosis (OS) risk. This cross-sectional study explores these associations in a large sample of older subjects with and without OSA.

METHODS: Volunteers were recruited from the PROgnostic indicator OF cardiovascular and cerebrovascular events survey. A total of 461 subjects, aged 68.7 ± 0.8 years, were examined, blood samples were taken, and they were subjected to home polygraphy, assessment of daily energy expenditure (DEE), and dual-energy X-ray absorptiometry.

RESULTS: Osteopenia (OP) was detected in 44% of subjects at the femoral and 39% at the vertebral level, while the prevalence of OS was lower at the femoral (4%) and vertebral (12%) levels. As expected, women had a higher prevalence of OP and OS. Subjects with OP and OS had a tendency to have lower DEE and values of obesity, apnea-hypopnea index (AHI), and indices of hypoxemia (ODI). At the correlation analyses, anthropometric factors and DEE were significantly related to BMD with a slight effect of indices of OSA severity. After adjustment for confounding variables, univariate and multivariate regression analyses showed a strong significant association between femoral and lumbar BMD and T-score and DEE without contribution of metabolic data and with a slight negative effect of respiratory factors.

CONCLUSIONS: In this sample of the elderly, physical activity was the best predictor of OS with a slight effect of body mass index. The indices of OSA confirm their protective effect on bone mineral density.