Increased postural sway in persons with multiple sclerosis during short-term exposure to warm ambient temperatures

Background Multiple sclerosis (MS) is a neurological disease marked by demyelination and axonal loss. Individuals with MS experience increases in clinical signs and symptoms during heat exposure. Objective To test the hypothesis that moderate heat exposure adversely affects postural sway in individuals with MS. Methods Ten individuals with relapsing-remitting MS (50 ± 8y) and nine controls (47 ± 10y) were examined under a Thermal and a Time Control trial. Following a 30 min thermoneutral baseline (25 °C, 30% relative humidity (RH)), stand tests randomized with eyes open and closed, were performed. For Thermal, subjects were first exposed to 60 min of heating (40 °C, 30%RH) followed by 60 min of cooling (20 °C, 30%RH). For Time Control, subjects remained in a thermoneutral environment throughout. Stand tests were repeated at consistent times in both trials. Results No difference in skin and core temperatures between groups were observed for any trial (P > 0.05). During heating, postural sway was higher in MS relative to control subjects (eyes open, P = 0.03; eyes closed, P = 0.011). No differences in postural sway, regardless of eye status, were observed during the Time Control trial for either group (P > 0.05). Conclusion These data demonstrate that exposure to a moderate heating environment increases postural sway in patients with MS.