MS often includes autonomic symptoms, although the disease effects on the autonomic nervous system (ANS) remain less characterized. Emotional distress is elevated in MS and can influence autonomic functioning. We evaluated HRV, an easily-obtained ANS biomarker, in relation to MS symptom burden.

Participants were: (1) people with MS and without history of cardiac disease consecutively recruited during the course of routine outpatient visits, and (2) healthy controls (HCs). Both MS and HCs participants completed two short-term (5-mins) EKG recordings and self-reported distress (Kessler Psychological Distress Scale, K10) and symptom ratings (SymptoMScreen, MFIS). HR signals were recorded using a portable, single-lead fingertip HR monitor (KardiaMobile). Short-term HRV was measured in a seated position and during spontaneous breathing. Time- and frequency-domain analyses of the HRV were performed. The following HRV parameters were obtained: (1) Square root of the mean squared differences between successive RR intervals (RMSSD), (2) high-frequency power (HF-HRV).

We recruited n=22 participants with MS (age: 51±11 years, 68% female, median PDSS: 3.0) and n=19 HCs  (age: 41±19 years, 47% female). Compared to HCs, the MS group had significantly lower RMSSD (24.3 ms vs. 39.8 ms, p=.002) and HF-HRV (32.6 nu vs. 45.1 nu, p=.001). Among the MS group, HF-HRV was significantly correlated with severity of symptoms (r=-.646, p=.001), fatigue (r=-.703, p<.001) and distress (r=-.527, p=.012). Distress predicted MS symptoms severity (r=.499, p=.018).

MS is associated with lower parasympathetic activity measured by reduced HRV, and HRV is linked with symptom severity. MS may lead to autonomic dysregulation, due both to factors of disease (axonal injury) and disease-related emotional distress. Further study is needed to develop HRV for clinical utility in MS.