Is season of birth associated with multiple sclerosis?

Objective - To compare the monthly distribution of multiple sclerosis (MS) patients' births with that of the Sicilian population. Background Studies o n the association between season of birth and risk of MS are scanty and con troversial. Design and methods - Archives of the Institute of Neuropsychiat ry of the Universities of Palermo and Catania were searched up to 1995 for definite MS patients (McDonald & Halliday criteria). The monthly distributi on of MS patients' births (N=965) was compared with that of the Sicilian po pulation (N=5,608,307). Results - The distribution of births among MS patie nts compared with the general population was not different when tested by t he chi(2) statistic (P>0.25). The Hewitt's non-parametric test for seasonal ity showed an excess of births between June and November among MS patients (P=0.004). Conclusion - A different pattern of MS patients' births is obser ved in Sicily and in Northern countries.