Multiple sclerosis and age at exposure to childhood diseases and animals: cases and their friends.

Eighty-eight multiple sclerosis case-friend pairs were interviewed by telephone to elicit information about early-life exposures. Available mothers were also interviewed. Risk factors included childhood diseases, exposures to animals, and residence. We found a positive association between MS and having measles at a later than usual age. Analysis of the data in the literature showed that this was the third statistically significant association between MS and later age for measles. This is consistent with the hypothesis that the pathogenesis of MS includes an age-dependent host response to measles.