Limited impact of the summer heat wave in France (2003) on hospital admissions and relapses for multiple sclerosis.

Patients with multiple sclerosis (MS) often report worsening of symptoms with increased environmental temperature. The aim of this paper was to determine whether or not the heat wave of the summer of 2003 in France was responsible for an increase in hospital admissions and relapses in MS patients. MS patients who were hospitalized between January 1,2000 and December 31,2003 were identified, and we established which patients were suffering relapses. Hospitalization and relapse seasonality were examined and analyzed according to ambient temperature variations. We did not observe a greater number of hospital admissions and relapses during the summer of 2003 compared to the previous 3 years. Results showed that MS hospitalizations display a significant trough in the winter season, especially in December, but no significant peak season or month was observed. There was no statistically significant correlation between mean ambient temperature and the number of admissions and relapses. The adverse symptoms associated with high temperatures that are usually observed in MS patients may require rapid rises in ambient temperate or in internal body temperature.