Multiple sclerosis (MS) damages the nervous system in ways that extend beyond the visible neurological symptoms. A 2025 meta-analysis combining 43 studies with 1,518 MS patients reveals the extent of autonomic dysfunction in this population[1].
The Meta-Analysis Evidence
The 2025 Acta Neurologica Belgica meta-analysis found significant reductions across all major HRV parameters in MS patients compared to healthy controls[1]:
RMSSD: SMD = -0.81 (p < 0.01) — substantial parasympathetic reduction
pNN50: SMD = -0.63 (p < 0.001) — another parasympathetic marker significantly affected
HF power: SMD = -0.51 (p < 0.01) — high-frequency vagal activity reduced
LF power: SMD = -0.44 (p < 0.05) — low-frequency power also lower
The RMSSD reduction (SMD = -0.81) is a large effect size — comparable to what we see in PTSD, which has among the most severe HRV reductions of any condition.
Progressive MS vs. Relapsing-Remitting MS
Not all MS is equal when it comes to autonomic function. Research consistently shows that progressive MS (primary progressive or secondary progressive) has worse autonomic damage than relapsing-remitting MS (RRMS)[2]:
Patients with progressive MS have a significantly higher burden of autonomic dysfunction compared to RRMS
SDNN, LF, and HF are all significantly lower in progressive MS (all p < 0.006)
Progressive MS patients show blunted sympathetic reactivity — they fail to show normal HRV changes during orthostatic challenge
Disease duration and disability level (EDSS score) are positively correlated with autonomic dysfunction
One study found that progressive MS patients showed no significant HRV change after head-up tilt testing (p = 0.8), while healthy controls and RRMS patients showed the expected responses[2]. This suggests the autonomic system progressively loses its flexibility as the disease advances.
The Prevalence of Cardiac Autonomic Dysfunction
A systematic review examining cardiac autonomic dysfunction (CAD) in MS found the prevalence is either 42% or 19%, depending on whether one or two abnormal autonomic tests are required for diagnosis[3]. Either way, autonomic problems are common.
Compared to healthy controls, MS patients show[4]:
Significantly lower RMSSD (21.86 ± 9.84 vs. 43.13 ± 20.98 ms, p = 0.002)
Significantly lower HF power (32.69 ± 12.01 vs. 42.39 ± 7.96 nu, p = 0.016)
Significantly higher LF/HF ratio — indicating altered sympathovagal balance
The roughly 50% reduction in RMSSD is substantial and indicates significantly compromised parasympathetic function.
HRV and MS Fatigue
Fatigue is one of the most disabling symptoms in MS, and it appears to be connected to HRV. Among MS patients, HF-HRV is significantly correlated with symptom severity (r = -0.548, p = 0.010)[5].
Patients with high levels of fatigue exhibit greater autonomic dysfunction, particularly reduced HRV that reflects parasympathetic activity. The proposed mechanism: fatigue might be the subjective representation of inflammatory processes, and the vagus nerve (which controls HRV) is intimately connected to immune regulation.
This creates a practical implication: HRV could serve as an objective correlate of symptom burden in MS. Rather than relying solely on self-report, HRV monitoring might help track disease impact.
Can Anything Help?
A 2023 RCT compared deep breathing and progressive muscle relaxation (PMR) in MS patients[6]:
Both relaxation exercises changed autonomic nervous system activity
Only the PMR group experienced a significant drop in fatigue
The vigilance task used to induce fatigue significantly reduced HRV parameters of parasympathetic activity
Yoga practices, which heavily rely on deep breathing, may be particularly helpful for alleviating MS-related fatigue by temporarily increasing parasympathetic activity[5]. The goal is restoring some parasympathetic balance.
Exercise also shows promise. A 2024 systematic review of 40 RCTs found that exercise interventions improve fatigue, balance, gait, and quality of life in MS patients[7]:
Tele-exercise showed significant improvements in fatigue (SMD = -0.58, p = 0.01)
High-intensity resistance training leads to clinically relevant fatigue reductions
Physical activity recommendations have evolved from caution to encouragement
Why MS Damages Autonomic Function
The mechanisms aren't fully understood, but several pathways are implicated:
Demyelination — MS attacks myelin throughout the CNS, including areas controlling autonomic function
Brainstem lesions — lesions in the brainstem directly affect cardiovascular control centers
Inflammation — the vagus nerve regulates inflammation via the cholinergic anti-inflammatory pathway; MS inflammation may impair this regulation
Progressive neurodegeneration — as axons are lost, autonomic control deteriorates
Disease activity during clinical relapses seems associated with sympathetic dysfunction, whereas disease progression appears linked with parasympathetic dysfunction, particularly in advanced stages[3].
Practical Implications
If you have MS:
Expect HRV values below population norms — don't compare yourself to healthy averages
Track your personal trends rather than absolute values
Fatigue levels may correlate with HRV — track both
Deep breathing exercises may help restore some parasympathetic tone
Exercise is beneficial, not harmful — the old "don't exert yourself" advice is outdated
For clinicians:
Progressive MS patients have significantly worse autonomic profiles than RRMS
HRV may serve as an objective marker of symptom burden
Orthostatic HRV testing may reveal blunted responses in progressive disease
Physical activity recommendations should include intensity guidance (HIRT shows benefits)
The Bottom Line
MS significantly reduces HRV, with effect sizes comparable to PTSD and heart failure. Progressive MS shows worse autonomic dysfunction than relapsing-remitting MS, and autonomic function appears to decline with disease duration and disability level.
The connection between HRV, fatigue, and inflammation in MS suggests that interventions targeting vagal tone (breathing exercises, yoga, exercise) may help manage symptoms. HRV monitoring could provide an objective way to track symptom burden alongside subjective reports.
Sources
1. Mirmosayyeb O et al. (2025). Heart rate variability in people with multiple sclerosis: A systematic review and meta-analysis. Acta Neurologica Belgica. accessibility.link.new-tab (43 studies, n=1,518 MS patients + 1,062 controls)