Objectives: To determine whether weather conditions explain the North-South gradient in multiple sclerosis (MS) mortality described in Spain.
Methods: The age-adjusted MS mortality rate by Spanish provinces from 1975 to 1998 was correlated with several climatic variables.
Results: MS mortality was negatively correlated with minimum, average and maximum temperatures, the mean number of hours of sunshine, and the mean number of sunny days. A positive correlation was found with the average amount of rain. Most correlations disappeared after adjusting by latitude. However, MS mortality was associated with latitude after adjusting by climatic factors.
Conclusions: The North-South gradient in MS mortality in Spain cannot be fully explained by weather differences. Therefore, other hypotheses are required to explain this association.