Association between beta-interferon exposure and hospital events in multiple sclerosis

PurposeA systematic evaluation of hospital events can be an important surrogate measure for drug effectiveness or adverse effects. The purpose of this study was to examine the association between beta-interferon use and hospital events in a large cohort of patients with multiple sclerosis (MS). MethodsRetrospective cohort study comparing beta-interferon exposed and unexposed patients using clinical data from the British Columbia MS (BCMS) database linked with health administrative databases, 1996-2008. For each patient, the primary outcome was the number of hospital events in each month, analyzed by quasi Poisson regression. Beta-interferon exposure was examined two ways: current and cumulative exposure. Secondary outcomes included whether a hospital event occurred in each month for each specific primary diagnoses, grouped by International Classification of Diseases categories. ResultsCurrent exposure to beta-interferon was not associated with an altered rate of hospital events (adjusted incident rate ratio 1.018; 95% CI 0.803-1.290). Similarly, there was no association with cumulative exposure. Cumulative beta-interferon exposure was associated with a lower odds of respiratory disease-related hospital events compared to those never exposed to beta-interferon. ConclusionsExposure to beta-interferon for MS was not associated with a change in overall hospital event rates. Preliminary evidence suggests that the beta-interferons may have a protective effect against respiratory diseases requiring hospitalization in MS patients. Copyright (c) 2014 John Wiley & Sons, Ltd.