The effects of heat stress on physical functioning in persons with multiple sclerosis

Heat sensitivity is a well-recognised feature in multiple sclerosis (MS). However, little is known about how heat affects physical performance in persons with MS. The objective of the study was to evaluate the effects of short-term heat stress on physical functioning in persons with MS. Twenty-three heat-sensitive MS subjects and 19 healthy controls participated. Moderate heat exposure took place in a dry Finnish sauna. Measures of upper and lower extremity function, static and dynamic balance, and walking capacity were applied. Core body temperature was measured by a telemetric physiological monitoring system. Assessments were conducted before, immediately, 1 hour, and 1 day after the heat exposure. Subjects with MS showed a significantly (P=0.002) higher core body temperature than the controls following the heat stress. Performances in walking (P<0.001), chair rise (P=0.005) and functional reach (P=0.04) were poorer in MS subjects than in controls immediately after the heat. No prolonged heat effects were observed. An increase in ambient temperature causes a higher core body temperature rise in MS subjects than in healthy controls. This rise in temperature is associated with acute, but not prolonged detrimental effects on physical functioning.