WESTPORT, Jul 13 (Reuters Health) - A population-based case-control study provides further support for antecedent infection as an etiologic factor in the onset of multiple sclerosis.
Dr. Ruth Ann Marrie of McGill University in Montreal, Quebec, Canada, and colleagues identified incident cases of multiple sclerosis in the computerized patient records that make up the UK General Practice Research Database.
A total of 225 cases of multiple sclerosis were identified from approximately 4 million subjects registered between 1990 and 1997. These cases were matched to 900 control subjects for sex, age, and physician practice. Results are reported in the June 27th issue of Neurology.
The risk of developing multiple sclerosis was associated with the frequency of respiratory tract infections at 5 weeks, 3 months and 12 months before the index date. "Exposure to respiratory tract infection in the 3 months before the index date was associated with more than double the risk of multiple sclerosis," the investigators write.
A history of infectious mononucleosis was associated with a 6-fold increased risk of subsequent multiple sclerosis when mononucleosis occurred after the age of 17 years.
"These results support an association between a history of infectious mononucleosis and subsequent MS," Dr. Marrie and colleagues conclude. "Respiratory tract infections may precipitate disease onset."