ObjectivesTo quantify the effect of hypoglossal nerve stimulation (HNS), a novel therapy for patients with obstructive sleep apnea, on objective level of alertness (measured with Maintenance of Wakefulness Test [MWT] values) and nocturnal sleep architecture.MethodsTen male patients (mean age 52.0 ± 9.4 years; mean body mass index 28.8 ± 3.3 kg/m²) noncompliant to continuous positive airway pressure received HNS (Inspire therapy) and were prospectively evaluated at baseline and 6 months after HNS therapy. Polysomnographic parameters (sleep breathing and sleep architecture) and objective level of alertness (MWT) were measured.ResultsThe mean preimplantation apnea-hypopnea index of 46.7/h ± 12.2/h was reduced to 14.5/h ± 8.9/h at 6 months postimplantation (p < 0.001). The mean MWT latency improved from 25.0 ± 12.8 minutes at baseline to 36.8 ± 7.0 minutes after 6 months of treatment (p = 0.004). A reduction of N1% (11.8 ± 10.6 vs 4.2 ± 1.9, p = 0.04) was observed. The reduction in the duration of wake after sleep onset (WASO) was 71.4 ± 32.4 minutes vs 53.4 ± 13.5 minutes (p = 0.06) but was not significant. MWT latencies at 6 months were negatively correlated with the intensity of stimulation (r = −0.63, p = 0.05). Intensity of stimulation was positively correlated with WASO (r = 0.76, p = 0.01).ConclusionHNS improved the objective level of alertness and changed nocturnal sleep architecture. The level of neural stimulation determines the amount of nocturnal WASO and the level of objective level of alertness.