PURPOSE: Sleep surgery and mandibular advancement devices (MAD) are treatments for obstructive sleep apnea (OSA), but their comparative efficacy remains unclear. We compared their efficacy using various parameters. METHODS: Subjects treated for OSA with sleep surgery or MAD (n = 30/group)-matched for sex, body mass index (BMI), and baseline apnea-hypopnea index (AHI)-were enrolled. The efficacy of these treatments according to polysomnographic parameters, sleep quality questionnaires, and heart rate variability (HRV) time- and frequency-domain parameters were compared between pre-treatment and 3-month post-treatment. RESULTS: Polysomnographic and sleep quality questionnaire parameters improved significantly in both groups. In time-domain HRV analysis, average normal-to-normal intervals increased significantly in the surgery (942.2 +/- 140.8 to 994.6 +/- 143.1, P = 0.008) and MAD (901.1 +/- 131.7 to 953.7 +/- 123.1, P = 0.002) groups. Low frequency (LF) decreased significantly in the surgery group (P = 0.012); high frequency (HF) remained unchanged in both groups. The LF/HF ratio decreased in both groups (2.9 +/- 1.8 to 2.3 +/- 1.7, P = 0.017, vs. 3.0 +/- 1.8 to 2.4 +/- 1.4, P = 0.025). Normalized high frequency increased significantly in both groups (31.0 +/- 13.2 to 36.8 +/- 13.7, P = 0.009, vs. 29.1 +/- 10.7 to 33.7 +/- 12.5, P = 0.024), in contrast to normalized low frequency. However, no HRV parameter changes differed significantly between the groups after adjusting for age, BMI, and AHI. CONCLUSION: Sleep surgery and MAD are equally effective treatments for OSA according to cardiac autonomic activity.