Open Access Highly Accessed Research article

A seasonal periodicity in relapses of multiple sclerosis? A single-center, population-based, preliminary study conducted in Bologna, Italy

Fabrizio Salvi1, Ilaria Bartolomei1, Michael H Smolensky2, Angelo Lorusso1, Elena Barbarossa1, Anna Maria Malagoni3, Paolo Zamboni3 and Roberto Manfredini345*

Author Affiliations

1 Department of Neuroscience, Multiple Sclerosis Center, Bellaria Hospital, Bologna, Italy

2 Department of Biomedical Engineering, the University of Texas at Austin, USA

3 Vascular Diseases Center, University of Ferrara, Italy

4 Department of Internal Medicine, Hospital of the Delta, Azienda Unità Sanitaria Locale, Ferrara, Italy

5 Department of Clinical and Experimental Medicine, Clinica Medica and Vascular Diseases Center, University of Ferrara, Italy

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BMC Neurology 2010, 10:105  doi:10.1186/1471-2377-10-105

Published: 1 November 2010



Temporal, i.e., 24-hour, weekly, and seasonal patterns in the occurrence of acute cardiovascular and cerebrovascular events are well documented; however, little is known about temporal, especially seasonal, variation in multiple sclerosis (MS) and its relapses. This study investigated, by means of a validated chronobiological method, whether severe relapses of MS, ones requiring medical specialty consultation, display seasonal differences, and whether they are linked with seasonal differences in local meteorological variables.


We considered 96 consecutive patients with severe MS relapse (29 men, 67 women, mean age 38.5 ± 8.8 years), referred to the Multiple Sclerosis Center, Bellaria Hospital, Bologna, Italy, between January 1, 2007 and December 31, 2008. Overall, we analyzed 164 relapses (56 in men, 108 in women; 115 in patients aged < 40 years, 49 in patients ≥40 years). Relapses were more frequent in May and June (12.2% each) and the least frequent in September (3.7%). Chronobiological analysis showed a biphasic pattern (major peak in May-June, secondary peak in November-December, p = 0.030). Analysis of monthly mean meteorological data showed a significant seasonal pattern in ambient temperature (peak in July, p < 0.001), relative humidity (peak in January, p < 0.001), and wind speed (peak in June, p = 0.011).


In this Italian setting, we found a biphasic pattern (peaks in spring and autumn) in severe MS relapses requiring medical consultation by doctors of the MS specialty center, apparently unrelated to meteorological variables. Confirmations of the findings on larger multi-center populations residing in different climatic conditions are needed to further explore the potential seasonality of MS relapses and associated environmental triggers.