Autonomic symptom burden is an independent contributor to multiple sclerosis related fatigue

To investigate a possible association between autonomic dysfunction and fatigue in people with multiple sclerosis.

In 70 people with multiple sclerosis early in the disease course (51 females, mean age 33.8 ± 9.1), quantitative sudomotor axon reflex tests, cardiovascular reflex tests (heart rate and blood pressure responses to the Valsalva maneuver and heart rate response to deep breathing), and the tilt table test were performed. Participants completed the Composite Autonomic Symptom Score 31, the Modified Fatigue Impact Scale, and the Epworth Sleepiness Scale, as well as the Beck Depression Inventory. Cutoff scores of ≥ 38 or ≥ 45 on the Modified Fatigue Impact Scale were used to stratify patients into a fatigued subgroup (N = 17 or N = 9, respectively).

We found clear associations between fatigue and scores in subjective tests of the autonomic nervous system: fatigued patients scored significantly worse on Composite Autonomic Symptom Score 31, and there was a strong correlation between the Modified Fatigue Impact Scale and the Composite Autonomic Symptom Score 31 (rs = 0.607, p < 0.001). On the other hand, we found only modest associations between fatigue and scores in objective tests of the autonomic nervous system: there was a clear trend for lower sweating outputs at all measured sites, which reached statistical significance for the distal leg and foot. We found weak correlations between the Modified Fatigue Impact Scale and the Valsalva ratio (rs = - 0.306, p = 0.011), as well as between the Modified Fatigue Impact Scale and quantitative sudomotor axon reflex tests of the forearm, proximal, and distal lower leg (rs = - 0.379, p = 0.003; rs = - 0.356, p = 0.005; and rs = - 0.345, p = 0.006, respectively). A multiple regression model showed that the Composite Autonomic Symptom Score 31, Beck Depression Inventory, and Epworth Sleepiness Scale were independent predictors of fatigue (p = 0.005, p = 0.019, and p = 0.010, respectively).

These results suggest that-even early in the course of the disease-people with multiple sclerosis suffer from objective and subjective impairments of the autonomic nervous system. The results also point to an association between autonomic nervous system impairment and multiple sclerosis related fatigue.