Clustering of residence of multiple sclerosis patients at age 13

Geographic and temporal vanation and migration studies point to an exogenous agent in the etiology of multiple sclerosis. If infectious etiology is involved, space-time clustering would also be expected. The authors analyzed 381 patients with a clinical onset of multiple sclerosis between 1953 and 1987 in the county of Hordaland, Norway Patients within the same birth cohort had lived significantly closer to each other than would be expected during ages 13-20 years, with peak clustering at age 18 years (p = 0.002) Clustering was also shown between patients in pairs compnsed of one individual with initial remittent disease and the other with chronic progressive course of disease, suggesting a similar etiology for both clinical patterns. Clustenng between cases with widely divergent dates of clinical onset provides evidence of marked vanation in latency No similar clustenng was observed in age-, sex-, and area-matched hospital controls without multiple sclerosis, and no clustenng was found among the cases when using fixed number of years before onset. These results are compatible with a common infectious agent, such as the Epstein-Ban- virus, acquired in adolescence in genetically vulnerable persons who are also not protected by an infection acquired before this ag