Adherence and persistence to drug therapies for multiple sclerosis: A population-based study.

OBJECTIVE: We aimed to estimate the prevalence and predictors of optimal adherence and persistence to the disease-modifying therapies (DMT) for multiple sclerosis (MS) in 3 Canadian provinces.

METHODS: We used population-based administrative databases in British Columbia (BC), Saskatchewan, and Manitoba. All individuals receiving DMT (interferon-B-1b, interferon-B-1a, and glatiramer acetate) between 1-January-1996 and 31-December-2011 (BC), 31-March-2014 (Saskatchewan), or 31-March-2012 (Manitoba) were included. One-year adherence was estimated using the proportion of days covered (PDC). Persistence was defined as time to DMT discontinuation. Regression models were used to assess predictors of adherence and persistence; results were pooled using random effects meta-analysis.

RESULTS: 4830 individuals were included. When results were combined, an estimated 76.4% (95% CI: 69.1-82.4%) of subjects exhibited optimal adherence (PDC ≥80%). Median time to discontinuation of the initial DMT was 1.9 years (95% CI: 1.6-2.1) in Manitoba, 2.8 years (95% CI: 2.5-3.0) in BC, and 4.0 years (95% CI: 3.5-4.6) in Saskatchewan. Age, sex and socioeconomic status were not associated with adherence or persistence. Individuals who had ≥4 physician visits during the year prior to the first DMT dispensation were more likely to exhibit optimal adherence compared to those with fewer (0-3) physician visits.

CONCLUSIONS: We observed adherence that is higher than what has been reported for other chronic diseases, and other non-population-based MS cohorts. Closer examination as to why adherence appears to be relatively better in MS and how adherence influences disease outcomes could contribute to our understanding of MS, and prove useful in the management of other chronic diseases.