Cardiac autonomic function during postural changes and exercise in people with multiple sclerosis: A cross-sectional study

Abstract

BackgroundPeople with multiple sclerosis (PwMS) often develop an autonomic dysfunction (AD), which onset should be assessed early at a subclinical level, as it may interfere with pharmacological treatments and exercise. ObjectiveTo evaluate basal cardiac autonomic tone, its modulations during sit-to-stand, sub-maximal exercise and recovery in PwMS without clinical overt AD and its relationships with fatigue perception. MethodsTwenty-three PwMS (55 ± 8 yrs [mean ± SD]; EDSS score 5.7 ± 1.3) and 20 age-matched healthy controls (HC; 55 ± 8yrs) were enrolled. ECG was digitally acquired during:1) sitting at rest (low sympathetic activation); 2) standing (light sympathetic activation); and 3) during light exercise (moderate sympathetic activation) and recovery. Parasympathetic and sympatho-vagal parameters of heart rate (HR) variability in time and frequency domains were calculated from beat series. ResultsHR was slightly but not significantly higher in PwMS compared to HC in all experimental conditions. Parasympathetic indexes were significantly lower (p < 0.05) in PwMS compared to HC during baseline sitting and post-exercise recovery, whereas sympathovagal parameters were similar in both groups. No correlation between autonomic tone and perceived fatigue was observed. ConclusionParasympathetic tone appears to be impaired in PwMS basal and post-exercise conditions, but not during postural challenge and exercise. In addition, AD does not affect perceived fatigue.