Beta-interferon protects multiple sclerosis patients against enhanced susceptibility to infections caused by poor air quality.

Background: The monthly multiple sclerosis relapse rate was studied from January 1995 to March 2001 from hospital records in Southwestern Finland as a retrospective open-label study.

Methods: The relapse rates of beta-interferon users and nonusers were compared to ambient air inhalable particle levels and viral infections in the population with logistic regression.

Results: In the non-user group, relapses were more frequent 1 month following the episodes when PM(10) was in the highest quartile [logistic regression odds ratio = 1.196 (95% CI = 1.019-1.404), p = 0.028] and following adenovirus epidemics in the general population [logistic regression odds ratio = 2.234 (95% CI = 1.013-4.926), p = 0.046]. PM(10) and virus infections had no significant effects in interferon users.

Conclusion: In addition to being antiviral, interferon also protected multiple sclerosis patients against an enhanced susceptibility to infections caused by PM(10).