Objective: To compare the monthly distribution of multiple sclerosis (MS) patients' births with that of the Sicilian population.
Background: Studies on the association between season of birth and risk of MS are scanty and controversial.
Design and methods: Archives of the Institute of Neuropsychiatry of the Universities of Palermo and Catania were searched up to 1995 for definite MS patients (McDonald & Halliday criteria). The monthly distribution of MS patients' births (N= 965) was compared with that of the Sicilian population (N= 5,608,307).
Results: The distribution of births among MS patients compared with the general population was not different when tested by the chi2 statistic (P> 0.25). The Hewitt's non-parametric test for seasonality showed an excess of births between June and November among MS patients (P=0.004).
Conclusion: A different pattern of MS patients' births is observed in Sicily and in Northern countries.