Adherence to disease‐modifying therapies for multiple sclerosis and subsequent hospitalizations

PurposeThe aim of this study was to examine the association between optimal adherence to first-line disease-modifying therapies (DMT) for multiple sclerosis (MS) and hospitalizations. MethodsWe used population-based administrative data from three Canadian provinces. All individuals receiving DMT (interferon-B-1b, interferon-B-1a, or glatiramer acetate) between January 1, 1996, and December 31, 2011 (British Columbia); March 31, 2012 (Manitoba); or March 31, 2014, (Saskatchewan) were included. Adherence was estimated for the first year of DMT (year 0), using the medication possession ratio (MPR). The association between optimal adherence (MPR80%) and all-cause and MS-specific hospitalizations in the subsequent 1, 2, and 5years was assessed using Hurdle Poisson and logistic regression. Rate and odds ratios were adjusted (aRR and aOR) for sociodemographic factors and prior health-care utilization. ResultsOverall, 4746 subjects were followed for a mean 7.8 (SD 4.0) years; 3598 (76%) were women. Optimal DMT adherence was achieved in 3564/4746 (75.1%) subjects. Subsequent all-cause and MS-specific hospitalizations were lower for subjects with optimal versus suboptimal adherence, but none reached statistical significance (1-year period, aRR=0.77, 95%CI: 0.47-1.26; aOR=0.80, 95%CI: 0.52-1.25). Similar findings were observed in the 2-year and 5-year periods. Prior health-care utilization (hospitalizations and medications) was associated with future hospitalizations; for every additional medication class, the 5-year all-cause hospitalization rate and likelihood of an MS-specific hospitalization increased by 5% and 11%, respectively (aRR=1.05, 95%CI: 1.02-1.07; and aOR=1.11, 95%CI: 1.07-1.14). ConclusionsHospitalization rates were lower in subjects with optimal DMT adherence, but findings were not statistically significant. Prior hospitalization and polypharmacy were associated with increased risk for future hospitalizations in MS. Copyright (c) 2017 John Wiley & Sons, Ltd.