Bone metabolism and fracture risk in obstructive sleep apnea

Background: Obstructive sleep apnoea (OSA) is a sleep disorder which might impact bone metabolism and increase fracture risk. Treatment with continuous positive airway pressure (CPAP) may improve both. Aim: To assess bone metabolism and fracture risk in patients with newly diagnosed OSA and evaluate the effect of a 12-month CPAP treatment. Materials and methods: 130 patients with OSA and 61 controls were included. Laboratory and instrumental researches and a test were performed. Fracture risk was assessed by FRAX (Fracture Risk Assessment Tool). After 12 months some markers of the bone metabolism were re-evaluated. Results: There is not a statistical difference in the age and sex in the OSA group compared to the controls (p>0.05 for both). Patients with OSA have significantly lower levels of vitamin D compared to the controls (19,8±11,67ng/ml vs. 36,13±21,65ng/ml; p<0,0001). There were significant differences in osteocalcin (OC) and beta-CrossLaps (beta-CTx), р<0.0001 for both. 43,1% of patients with OSA have 3 risk factors for osteoporosis, compared to 8,2% of the controls (р<0.0001). FRAX for large osteoporotic fractures in OSA was moderate, although it did not differ statistically from the risk in the controls (11.5±8.4% in OSA vs. 8.85±5.8% in controls, p=0.63). After 12 months there was a statistical change in levels of vitamin D (p <0.0001), OC (p <0.0001) and beta-CTx (p <0.012) compared to the baseline values. Conclusion: OSAS patients have an abnormal bone metabolism, average of 3 risk factors for osteoporosis and moderately increased fracture risk. CPAP treatment improves bone metabolism and reduces fracture risk.