Neuroadrenergic activation in obstructive sleep apnoea syndrome: A new selectedmeta-analysis - revisited

Background: Neuroadrenegic overdrive occurs in obstructive sleep apnoea syndrome (OSAS). However, the small sample size of the microneurographic studies, heterogeneity of the patients examined, presence of comorbidities, represented major weaknesses not allowing to precisely define the main features of the phenomenon, particularly in nonobese patients. Objective: This meta-analysis detected 14 microneurographic studies based on muscle sympathetic nerve activity (MSNA) quantification in uncomplicated OSAS of different clinical severity. Methods: The evaluation was extended to the relationships of MSNA with heart rate, anthropometric and blood pressure values, metabolic variables, apnoeahypopnea index and oxygen saturation. Results: MSNA is activated markedly and almost homogeneously between studies, showing a progressive increase from the healthy state to mild, moderate and severe OSAS (46.03, 48.32, 71.84, 69.27 bursts/100 heart beats). Of special interest are the findings that MSNA is significantly related to the apnoea-hypopnea index, a marker of OSAS severity (r 0.55, P 0.04) but not to BMI, as it occurs in OSAS associated with obesity, and heart rate is significantly and directly related to MSNA and apnoea-hypopnea index (r 0.68 and r 0.60, respectively P 0.03 and P 0.02), thus representing a surrogate marker of the sympathetic overdrive. Conclusion: OSAS, even when uncomplicated by other cardiometabolic disease, displays a marked sympathetic activation, reflected by the MSNA and heart rate behaviour, becoming a target of therapeutic interventions aimed at exerting sympathomoderating effects, such as continuous positive airway pressure.