Clustering during childhood of multiple sclerosis patients

Previous studies investigating the possibility of space-time clustering in multiple sclerosis (MS) used time and place of onset of the disease or time and place of birth of the MS patient as the testing point. However, immigration studies have shown that the risk of MS is determined during childhood and thus, ‘exposure’ probably occurred at sometime between birth and age 15. In this study it was possible to study space-time clustering at any time during childhood.Of 222 MS patients identified in an intensive prevalence survey in Ottawa, Canada, 97 had spent their childhood in Ottawa. All exact addresses prior to age 15 were obtained and pinpointed on the map. Two clustering tests were used: one developed by Knox and the generalized regression approach by Mantel, but no clustering could be detected at any stage of childhood. Such a lack of clustering does not rule out a viral etiology, but does require us to modify our thinking with respect to mechanism of transmission of the disease.