The effect of obstructive sleep apnea therapy on cardiovascular autonomic function: a systematic review and meta-analysis

STUDY OBJECTIVES: Autonomic function is impaired in obstructive sleep apnea (OSA) and may mediate the association between OSA and cardiovascular risk. We investigated the effect of OSA therapy on autonomic function through a systematic review and meta-analysis of intervention studies. METHODS: A systematic search using three databases (Medline, Embase, and Scopus) was performed up to December 9, 2020. Studies of OSA patients ≥ 18 years with autonomic function assessed before and after treatment with positive airway pressure, oral appliance, positional therapy, weight loss, or surgical intervention were included for review. Random effects meta-analysis was carried out for five groups of autonomic function indices. Risk of bias was assessed using the Cochrane Collaboration tool. RESULTS: Forty-three eligible studies were reviewed with 39 included in the meta-analysis. OSA treatment led to large decreases in muscle sympathetic nerve activity (Hedges’ g = −1.08; 95% CI −1.50, −0.65, n = 8) and moderate decreases in catecholamines (−0.60; −0.94, −0.27, n = 3) and radio nucleotide imaging (−0.61; −0.99, −0.24, n = 2). OSA therapy had no significant effect on baroreflex function (Hedges’ g = 0.15; 95% CI −0.09, 0.39, n = 6) or heart rate variability (0.02; −0.32, 0.36, n = 14). There was a significant risk of bias due to studies being primarily non-randomized trials. CONCLUSIONS: OSA therapy selectively improves autonomic function measures. The strongest evidence for the effect of OSA therapy on autonomic function was seen in reduced sympathetic activity as assessed by microneurography, but without increased improvement in parasympathetic function. OSA therapy may reduce the risk of cardiovascular disease in OSA through reduced sympathetic activity.