Nonadherence in MS Medications Associated with Age, Hospitalization History, and Copayments

San Francisco—A retrospective study of patients with multiple sclerosis (MS) found that nonadherence to disease-modifying drugs (DMDs) was associated with younger age, a history of a hospitalization or emergency department (ED) visits, and higher copayments. The results from the study, which relied on claims data, were presented in a poster session at the AMCP meeting. The poster was titled Risk Factors Associated with Nonadherence of Disease-Modifying Drugs among Patients with Multiple Sclerosis.

It is estimated that MS affects approximately 400,000 people in the United States. Previous research has found that adherence to DMDs can decrease risk of relapse, increase quality of life, and decrease costs, yet according to the authors of this latest study, adherence rates range from 28% to 87%. The reasons why some patients are not adherent to medications is not fully understood.

In this study, researchers used claims data to identify demographic and claims-based variables that may be associated with nonadherence to DMDs in newly diagnosed patients who had been prescribed self-injectable DMDs.

They identified newly diagnosed patients who had at least 1 medical claim with Medco Health Solutions for MS between 2006 and 2009 and no MS claims in the 12 months prior. To be included in the study, patients must have been ≥18 years of age, have filled at least 1 prescription for a DMD during the year, and have at least 12 months of continuous enrollment both before and after their first DMD prescription.

Medication adherence was assessed using proportion of days covered (PDC) and the medication possession ratio (MPR). Patients were considered nonadherent if they had a PDC <0.80 and MPR <0.80.

Researchers compared demographics, clinical characteristics, resource use, and out-of-pocket copayments between those who were adherent to DMDs and those who were not. They found that the baseline demographic characteristics were similar between patients in each annual cohort and reported the findings from the 2769 patients in the 2009 cohort, 62.3% of whom were found to be adherent using the PDC.

When assessing the differences between the nonadherent and adherent patients, researchers found that nonadherent patients were significantly younger than those who were adherent (47.5 vs 50.6 years, P<.05).

They also reported that nonadherent patients had hospitalization rates of 12.4% compared with 8.6% for adherent patients in the year before the first prescription was filled (P<.001).The rate of ED visits was also higher in the year before the index date for nonadherent patients (18.3% vs 14.3% for adherent patients, P<.05).

Using regression analyses, researchers found that when they used a model with PDC <0.80 as the outcome, nonadherence decreased with age and pain, while urinary problems were more likely to increase nonadherence. Other predictors of nonadherence using this model were copayments ≥$200 and hospitalization or ED visits before the initial DMD prescription was filled.

When researchers used a regression model with MPR <0.80 as the outcome, they found that the likelihood of nonadherence once again decreased with age. However, they also found that the region of the country where a patient resided played a role in nonadherence, with an association between nonadherence and living in the South or West. Under this model, they also reported that patient adherence was associated with outpatient visits in the year before the initial DMD prescription was filled.

The authors of the study acknowledged several limitations including using 1 database as the source for the study data, possible differences in the treatment group undetected through database variables, or possible inaccuracies in coding.

This study was supported by EMD Serono, Inc.