Medication adherence in multiple sclerosis as a potential model for other chronic diseases: a population-based cohort study.

To determine whether better medication adherence in multiple sclerosis (MS) might be due to specialised disease-modifying drug (DMD) support programmes by: (1) establishing higher adherence in MS than in other chronic diseases and (2) determining if higher adherence is associated with patient-specific or treatment-specific factors. Retrospective cohort study with data from 1 January 1996 to 31 December 2015. Population-based health administrative data from three Canadian provinces. Individual cohorts were created using validated case definitions for MS, epilepsy, Parkinson's disease (PD) and rheumatoid arthritis (RA). Subjects were included if they received ≥1 dispensation for a disease-related drug between 1 January 1997 and 31 December 2014. Proportion of subjects with optimal adherence (≥80%) measured by the medication possession ratio 1 year after the index date (first dispensation of disease-related drug). 126 478 subjects were included in the primary analysis (MS, n=6271; epilepsy, n=55 739; PD, n=21 304; RA, n=43 164). Subjects with epilepsy (adjusted OR, aOR 0.29; 95% CI 0.19 to 0.45), PD (aOR 0.42; 95% CI 0.29 to 0.63) or RA (aOR 0.26; 95% CI 0.19 to 0.35) were less likely to have optimal 1-year adherence compared with subjects with MS. Within the MS cohort, adherence was higher for DMD than for chronic-use non-MS medications, and no consistent patient-related predictors of adherence were observed across all four non-MS medication classes, including having optimal adherence to DMD. Subjects with MS were significantly more likely to have optimal 1-year adherence than subjects with epilepsy, RA and PD, and optimal adherence appears related to treatment-specific factors rather than patient-related factors. This supports the hypothesis that higher adherence to the MS DMDs could be due to the specialised support programmes; these programmes may serve as a model for use in other chronic conditions.

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Déclaration de conflit d'intérêts

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: CE reports grants from Canadian Institutes of Health Research during the conduct of the study; RAM reports grants from Canadian Institutes of Health Research during the conduct of the study; HT reports grants from Canada Research Chair for Neuroepidemiology and Multiple Sclerosis, grants from National Multiple Sclerosis Society, grants from Canadian Institutes of Health Research, other from National MS Society (2016, 2018), other from ECTRIMS-ACTRIMS (2016, 2017, 2018, 2019, 2020), other from American Academy of Neurology (2016, 2019), grants and other from the MS Society of Canada, outside the submitted work; DB is the Chair in Patient Adherence to Drug Therapy within the College of Pharmacy and Nutrition, University of Saskatchewan. This position was created through unrestricted financial support from AstraZeneca Canada, Merck Canada, Pfizer Canada and the Province of Saskatchewan’s Ministry of Health. None of the sponsors were involved in developing this study or writing the manuscript; no other relationships or activities that could appear to have influenced the submitted work. SY, FZ, RW and EK have nothing to disclose.