Fatigue in MS Linked to Elevated Body Temperature
This cross-sectional study has revealed that elevated body temperature is associated with fatigue in relapsing-remitting multiple sclerosis, even in the absence of heat exposure
Elevated body temperature is associated with fatigue in patients with relapsing-remitting multiple sclerosis (RRMS), even without exposure to external sources of heat, according to a cross-sectional study published online February 19 in the Archives of Physical Medicine and Rehabilitation (Sumowski and Leavitt, 2014).
James F. Sumowski, Ph.D., from Neuropsychology and Neuroscience, Kessler Foundation, West Orange, New Jersey, and the Department of Physical Medicine and Rehabilitation, Rutgers, New Jersey Medical School, Newark, and Victoria M. Leavitt, Ph.D., from the Manhattan Memory Center, New York City, note that exposure to external sources of heat has long been known to increase fatigue in patients with MS. However, no one has investigated whether body temperature is increased endogenously (i.e., without exposure to heat) and whether such increases might be linked to fatigue in RRMS.
These investigators studied 112 subjects: 50 patients with RRMS, 22 patients with secondary-progressive MS (SPMS), and 40 healthy control patients.
Pairwise comparisons showed significantly higher body temperatures among patients with RRMS (mean ± standard deviation, 37.04°C ± 0.27°C) relative to healthy control patients (36.83°C ± 0.33°C; P = 0.009) and patients with SPMS (36.75°C ± 0.39°C; P = 0.001). There was no statistically significant difference in temperatures between healthy control participants and patients with SPMS, the authors note.
Patients with RRMS were mostly women who had neither experienced an exacerbation during the previous 6 weeks nor were taking corticosteroids or antipyretics. Patients in the SPMS group met the same inclusion criteria.
Participants in the RRMS and control groups were in their mid-40s, with mean disease duration of 12.8 ± 8.0 years. The mean age of the participants in the SPMS group was 53.8 ± 7.4 years; disease duration was 17.6 ± 7.4 years.
The investigators recorded participants' core body temperatures, and in the patients with RRMS, they used both the Fatigue Severity Scale (FSS) and the Modified Fatigue Impact Scale (MFIS) to assess fatigue.
Patients with RRMS reported higher levels of general fatigue on the FSS as well as elevated levels of physical fatigue and cognitive fatigue on the MFIS. Warmer body temperatures among patients with RRMS were associated with higher self-reported general fatigue on the FSS and physical fatigue on the MFIS, but not cognitive fatigue on the MFIS.
The researchers said this is the first time it has been demonstrated that body temperature is elevated in patients with RRMS relative to healthy control patients and to patients with SPMS. It is also the first time elevated body temperatures have been positively linked to increased fatigue in patients with RRMS, they said.
They added that their findings might help explain why cooling garments and antipyretics tend to reduce fatigue in patients with MS.
Key open questions
- In patients with RRMS, could inflammation alone be sufficient to elevate body temperature, or are other factors likely to contribute?
- Might variations in age, menstrual cycles, and food and/or alcohol intake have been responsible for at least some of the increases in body temperature observed in this study?
- Given that in the RRMS group a link was observed between increased temperature and general and physical fatigue, why was no correlation seen with cognitive function?
Funding for this project was provided in part by the National Institutes of Health and the Kessler Foundation Research Center. Neither of the authors has reported conflicts of interest.