A Cochrane review [Abstract] 1 included 17 studies with a total of 831 patients. All the studies had some shortcomings. Oral appliances (OA) were less effective than continuous positive pressure (CPAP) in reducing apnoea-hypopnoea index (parallel group studies: 9.08 events/hr, 95% CI 4.78 to 13.38, statistical heterogeneity I2 59%, 4 studies; crossover studies: WMD 7.97 events/hr, 95% CI 6.38 to 9.56; 7 studies). No significant difference was observed on symptom scores. CPAP was more effective at improving minimum arterial oxygen saturation during sleep compared with OA. In two small crossover studies, participants preferred OA therapy to CPAP. Compared to control devices, oral appliances reduced daytime sleepiness in two crossover trials (ESS score -1.81; 95%CI -2.72 to -0.90), and improved apnoea-hypopnoea index AHI (-10.78 events/hr; 95% CI -15.53 to -6.03; parallel group data, 5 studies). Compared to corrective upper airway surgery (1 study), symptoms of daytime sleepiness were initially lower with surgery, but the difference disappeared at 12 months. AHI did not differ significantly initially, but did so after 12 months in favour of OA.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment).
A systematic review 2 included 5 studies. Comparing OA and control appliance, OA significantly reduced WMD in both AHI and the arousal index (favouring OA, AHI: -7.05 events h(-1) ; 95% CI -12.07 to -2.03; p = 0.006, arousal index: -6.95 events h(-1) ; 95% CI, -11.75 to -2.15; p = 0.005). OAs were significantly less effective at reducing the WMD in AHI and improving lowest SpO2 and SF-36 than CPAP, (favouring OA, AHI: 6.11 events h(-1) ; 95% CI, 3.24 to 8.98; p = 0.0001, lowest SpO2 : -2.52%; 95% CI, -4.81 to -0.23; p = 0.03, SF-36: -1.80; 95% CI, -3.17 to -042; p = 0.01). AHI and arousal index were significantly improved by OA relative to the untreated disease. AHI, lowest SpO2 and SF-36 were significantly better with CPAP than with OA.
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