AT AES 2016

HOUSTON (FRONTLINE MEDICAL NEWS) – One in three older Americans with epilepsy had poor adherence to antiepileptic drugs, according to a large retrospective study, and the numbers were even worse for members of minority populations.

In an analysis of Medicare claims, patients who were African American had an odds ratio of 1.56 (95% confidence interval, 1.46-1.68) for being non-adherent to antiepileptic drugs (AEDs). For Hispanic patients, the OR was 1.40 (95% CI, 1.28-1.54), while for Asians, the OR was 1.41 (95% CI, 1.25-1.54).

“Overall, 31.8% were non-adherent to AEDs; range was from 24.1% for whites to 34.3% for African Americans,” wrote Maria Pisu, PhD , and her collaborators in an abstract accompanying the poster presented at the annual meeting of the American Epilepsy Society.

The reasons for poor adherence are unknown, but warrant further investigation, said Dr. Pisu of the division of preventive medicine at the University of Alabama at Birmingham.

Dr. Pisu and her coinvestigators assessed AED adherence among older patients by examining administrative claims for Medicare beneficiaries aged 66 and older during 2008-2010. In addition to including a random sample of 5% of all older Medicare patients with epilepsy, the investigators also included all African American, Asian, Hispanic, American Indian, and Alaskan Native patients who had more than one ICD-9 code for seizure or epilepsy and had been prescribed at least one AED.

The sample included 36,912 patients with epilepsy. In the enhanced sample, 19.2% of patients were white, 62.5% were African American, 11.3% were Hispanic, 5.0% were Asian, and 2.0% were American Indian or Alaskan Native. Of the sample, 61.6% were female; 41.5% of patients were aged 66-74 years; 36.1% were aged 75-84 years; and 22.4% were 85 years or older.

In order to determine whether patients with epilepsy or seizures were adherent, investigators looked at the ratio of days that at least one AED prescription was in the database for a given patient, divided by the total days of follow-up on record (“proportion of days covered”). The primary outcome measure of nonadherence was defined as a proportion of days covered of less than 0.80.

Most patients had one to several comorbidities: only 8.3% had no other comorbidities, while 46.0% had more than four. The remainder fell somewhere in the middle.

A majority of patients (59.2%) had some form of copay or coinsurance for prescriptions. About half of patients (50.2%) lived in the South.

Through multivariable analysis, the investigators explored the relationships between nonadherence and race or ethnicity, demographics, geographic area of residence, comorbidities, and whether the prescribed AEDs were enzyme-inducing. Additionally, socioeconomic status was estimated by factoring in eligibility for Medicare Part D low income subsidies and using zip code–level poverty data.

The differences between ethnic groups, wrote Dr. Pisu, were significant “after accounting for several factors that affect prescription-taking factors, e.g., economic constraints,” so it was not just low socioeconomic status that accounted for the discrepancy.

The retrospective claims-based study was limited by several factors, wrote Dr. Pisu and her colleagues. True adherence is difficult to quantify, and may be overestimated by measuring filled prescriptions; on the other hand, some patients may have had other insurance coverage, and obtained medication through a means not captured in the study. Finally, dose adjustments may mean patients can “stretch” medications, thereby remaining adherent without refilling prescriptions.

Still, the study shows that nonadherence is pervasive among older Americans with epilepsy, with worse adherence among members of minority populations. “Interventions to promote adherence are important. These should account for the impact of drug cost-sharing and socioeconomic status on epilepsy treatment,” wrote Dr. Pisu.

The study was funded by the National Institute of Neurological Disorders and Stroke. Dr. Pisu reported no relevant financial disclosures.

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