Older adults with dual Medicare-Medicaid eligibility who presented to the hospital with MI had better rates of medication adherence compared with those who were eligible only for Medicare, according to a retrospective study.

However, the dual eligible had higher rates of 30-day readmissions, death at one year and major adverse cardiovascular outcomes at one year.

Lead researcher Jacob A. Doll, MD, of the Duke Clinical Research Institute and Duke University, and colleagues published their results online in JAMA Cardiology on Aug. 17.

Nearly six million adults in the U.S. are eligible for Medicare and Medicaid, according to the researchers. They added that dual eligibles typically have more chronic diseases and higher healthcare utilization than adults who are only eligible for Medicare.

The researchers identified 17,419 Medicare patients who were discharged alive after MI and enrolled from July 1, 2007, to Dec. 31, 2009, in the ACTION Registry-GWTG, the largest quality improvement registry of patients with MI in the U.S. They linked the patients to Medicare claims data and obtained one-year follow-up and medication adherence data.

Of the patients, 27 percent were dual eligible. All dual eligible patients and 11 percent of Medicare-only patients received a low income subsidy. Dual eligible patients were more likely to be female and nonwhite and to have a greater prevalence of comorbid conditions such as hypertension, diabetes and kidney disease.

Dual eligible patients had less frequent revascularization for non-ST elevation MI and primary PCI for ST elevation MI and used drug-eluting stents less often than Medicare-only patients.

At one year, nearly two-thirds of dual-eligible patients were readmitted to the hospital and nearly one-third had a major adverse cardiovascular event. The researchers defined readmission as the first hospitalization after index discharge and major adverse cardiovascular events as death, readmission for MI or stroke at one year.

After adjusting for differences in patient characteristics and in-hospital treatments, dual eligibility status was associated with a 16 percent higher risk of readmission at 30 days, a 24 percent higher risk of death at one year and a 21 percent higher risk of major adverse cardiac events at one year. The differences in one-year mortality between dual eligible and Medicare-only patients were present in subgroups based on age, sex, race and MI type.

Of the patients who survived for a year after discharge and enrolled in Medicare Part D coverage for the full year, only 50 to 60 percent were adherent to each of the four classes of medications prescribed at discharge. However, dual eligible patients were more likely to adhere to each medication.

“Despite these data, there may be a perception among clinicians that dual-eligible patients are less likely to adhere to medications owing to cost,” the researchers wrote. “This may contribute to lower usage rates of revascularization and drug-eluting stents, owing to concerns about discontinuation of dual-antiplatelet therapy. Our analysis indicates that these concerns should not be limited to the dual-eligible population. Nonadherence is common for all patients, and interventions to improve adherence should be applied uniformly.”

The researchers cited a few potential limitations of the study, including that they could not determine if dual eligibility, low socioeconomic status or the low income subsidy were causally related to the outcomes. They also could not rule out unmeasured confounders.

In addition, hospitals in this study participated in a national quality improvement registry, so the results might not be relevant for other hospitals. Further, the trial did not evaluate the expansion for Medicaid due to the Affordable Care Act.

“Despite the additional support provided by Medicaid coverage, dual-eligible older adults are a vulnerable population that may benefit from interventions to optimize post-myocardial infarction outcomes, including efforts to improve use of evidence-based therapies in the hospital and at the time of discharge,” the researchers wrote.