Association of obstructive sleep apnea with bone metabolism in older adults: a hospital-based study

PurposeObstructive sleep apnea (OSA) significantly affects patients' quality of life; however, the mechanisms, such as its effects on bone mineral density (BMD) and bone turnover marker (BTM) expression, remain unclear. In this study, we investigated the relationships among OSA, BMD, and (BTMs) in older adults. MethodsThis retrospective study enrolled 260 participants (114 women; 44.5%). Data of an established system (Alice NightOne) were used to diagnose OSA and analyze nocturnal hypoxia. Participants were divided into four groups according to respiratory event index (REI) (control, < 5 times/hour; mild OSA, 5-15 times/hour; moderate OSA 15-30 times/hour; severe OSA >= 30 times/hour). BMD were mesured by dual-energy x-ray absorptiometry. BTMs including bone specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase 5b (TRAP-5b) were collected. ResultsPatients with OSA had higher BMD at first lumbar vertebra, left and right femur than those without (all p < 0.05). REI was positively correlated with BMD at the first lumbar vertebra (r = 0.181, p = 0.006), left femur (r = 0.160, p = 0.014), and right femur (r = 0.243, p < 0.001). In participants with body mass index (BMI) of 18-24 kg/m(2) (N = 96), the correlation between REI and BMD at the left femur(r = 0.251, p = 0.019) and right femur (r = 0.258, p = 0.018) remained. Multiple regression analysis showed that OSA was significantly associated with osteoporosis (p = 0.034, 95% confidence interval, 0.092-0.100, odds ratio, 0.092). MSaO(2) was positively correlated with TRAP5b (r = 0.560, p = 0.007). In participants with a BMI of >= 24 kg/m(2)(N = 164), MSaO(2) was negatively correlated with BALP (r = -0.331, p = 0.034). No significant association between REI and BMD was observed. ConclusionsOSA and hypoxia were associated with higher BMD in older adults in BMI of 18-24 kg/m(2) but not in participants with a BMI of >= 24 kg/m(2). This study suggests a negative association between OSA and osteoporosis in non-overweight and obese population. BMI played an important role. The study's findings could help exploration mechanisms of osteoporosis and promoting its treatment.