Higher Rates of Medication Adherence Seen in MS Compared With Other Chronic Diseases

According to research published in BMJ Open, patients with multiple sclerosis (MS) are more likely to have optimal 1-year treatment adherence to MS disease-modifying drugs (DMDs) compared with individuals with epilepsy, rheumatoid arthritis (RA), and Parkinson disease (PD) taking their respective disease-specific drugs.

Results of the retrospective cohort study found that high adherence rates were due largely to treatment-specific factors as opposed to patient-related factors, supporting the hypothesis that specialized support programs lead to higher adherence and could serve as a model for use in other chronic conditions, authors said.

In 2009, a World Health Organization report estimated that only 50% of individuals with chronic disease were adherent to their medications, while in the United States, annual costs of medication nonadherence are estimated to be between $100 billion and $290 billion. “Reviews of the literature estimate 33%–88% of individuals with MS, 20%–75% with epilepsy, 30%–80% with RA and 10%–67% with PD have good adherence to their disease-specific medications,” researchers wrote.

Using similar population-based cohorts, methodology, and outcomes representing 3 Canadian provinces, researchers compared adherence to DMDs in MS with adherence to disease-specific medications among patients with PD, RA, and epilepsy. In addition, “as adherence can be influenced by many different factors, we examined adherence to chronic-use non-DMD medications in the MS cohort to determine if the higher adherence was associated with patient-related or treatment-specific factors,” they wrote.

Investigators analyzed health administrative data, including demographic information, hospital separations, physician services, and prescription drug dispensations from Manitoba (MB), Saskatchewan (SK), and British Columbia (BC) recorded between January 1996 and December 2014 (BC) or December 2015 (MB, SK).

All patients included in the study had at least 1 dispensation for a specific disease-related drug between January 1, 1997, and December 31, 2014, and “the date of the first dispensation after January 1, 1997, for a disease-related drug was defined as the index date.” Patients with MS who took HMG-CoA reductase inhibitors, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), and thyroid hormone replacement therapies were included in the secondary analysis.

The first year of therapy has been recognized as the most critical time for nonadherence in chronic diseases, researchers explained. “Adherence was estimated using the medication possession ratio (MPR), calculated as the sum of the days’ supply for all study drug dispensations during the observation period divided by the number of days in the observation period,” and an MPR of 80% or greater was considered optimal.

A total of 126,478 patients (n = 6271 for MS; 55,739 for epilepsy; 21,304 for PD; 43,164 for RA) were included in the primary analysis. Of those in the MS cohort who did or did not receive a DMD during the study period (n = 28,176), 13,780 subjects were identified as receiving at least 1 dispensation for a statin (n = 4628), ACEI (n = 4569), ARB (n = 1971), or thyroid replacement (n = 2612) medication.

Analyses revealed:

• The proportion of patients with optimal adherence (MPR) at 1 year was highest for the MS cohort (77.2%; 95% CI, 72.4%-81.3%), followed by PD (61.0%; 95% CI, 54.9%-66.8%), epilepsy (50.9%; 95% CI, 42.5%-59.3%), and RA (47.0%; 95% CI, 45.4%-48.8%).
• After adjustment, patients with MS were more likely to have optimal adherence than patients with PD (aOR 0.42; 95% CI, 0.29-0.63), epilepsy (aOR 0.29; 95% CI, 0.19-0.45), or RA (aOR 0.26; 95% CI, 0.19-0.35) at 1 year.
• Within the MS cohort, 1-year adherence was highest for patients who took DMDs (77.2%; 95% CI, 72.4%-81.3%), with a statistically significant difference seen for ARBs (60.3%; 95% CI, 56.7%-63.8%), statins (55.3%; 95% CI, 51.0%-59.4%) and ACEIs (54.7%; 95% CI, 53.3%-56.2%).
• Optimal 1-year adherence to DMDs was associated with increased odds of optimal 1-year adherence to a non-MS medication class, but only reached statistical significance for ACEIs (aOR 1.83; 95% CI, 1.23-2.71).

“Early discontinuations appeared to be a major reason for non-adherence, as up to 30% of subjects discontinued all antiepileptics or RA medications within the first 6 months of therapy,” researchers said.

In all disease cohorts, adherence levels decreased as more time passed since initiation, and the decrease was greatest in the MS cohort. This could be due to the lack of a consensus regarding how long individuals with MS should be treated with DMDs: As MS progresses in these patients, inflammation reduces and current DMDs can become less effective.

However, researchers hypothesized that the unique factor resulting in higher adherence to DMDs may be specialized DMD management and support programs provided by pharmaceutical companies to patients with MS in Canada. “These programs are often led by nurse educators, and provide individualized training, and ongoing support and follow-up at no-cost to individuals…These DMD support programs differ from most existing adherence interventions in that they provide comprehensive and continuous support,” authors wrote.

A lack of data on disease severity and potential adverse effects marks a limitation to the study, in addition to the absence of a variable specifically measuring comorbidity. Future research into DMD adherence and the effects of access to and quality of these programs ought to be carried out in order to better understand their potential use in other chronic conditions, the authors concluded.

Reference

Evans C, Marrie RA, Yao S, et al. Medication adherence in multiple sclerosis as a potential model for other chronic diseases: a population-based cohort study. BMJ Open. Published online February 5, 2021. doi:10.1136/bmjopen-2020-043930