Fatigue and heat sensitivity in patients with multiple sclerosis

Fatigue is one of the most common and troubling symptoms of multiple sclerosis (MS), and heat is often reported as a trigger. Although it is assumed that this heat sensitivity is specific for MS, the evidence for disease specificity is limited. We studied the relationship between fatigue, heat sensitivity, and environmental temperature, and its specificity for MS.

We compared 88 MS patients with 76 patients with ulcerative colitis (UC), another chronic auto-immune disease. As most important outcome measures, heat sensitivity, physical fatigue, mental fatigue, environmental temperature, and ambient UV-light levels were determined.

More patients with MS reported heat sensitivity for fatigue, compared to patients with UC (53.4% vs 35.5%, respectively, P = 0.016). However, heat-sensitive patients were equally fatigued as heat-insensitive patients. Climatological data, including day temperature and amount of ambient UV light, were not related to fatigue in both heat-sensitive and heat-insensitive patients with MS.

Our findings support the assumption that heat sensitivity regarding fatigue has an MS-specific component. Although patients with MS experience a relationship between environmental temperature and fatigue, objective assessment by climatological data could not confirm this.