Medicare Part D beneficiaries with no financial assistance who fall in the coverage gap known as the “donut hole” are 57 percent more likely to discontinue cardiovascular (CV) medications, according to a study published online April 17 in Circulation: Cardiovascular Quality and Outcomes. The researchers added that it was unclear whether these lapses affected long-term outcomes.

Annually, approximately 3.8 million Medicare Part D beneficiaries reach the limit where their prescription drugs are no longer covered under Medicare Part D, wrote Jennifer M. Polinski, ScD, MPH, an epidemiologist at Brigham and Women’s Hospital in Boston, and colleagues. Based on current Medicare rules, these beneficiaries are responsible for the entire cost of medications until they hit a spending threshold amount, at which point their drug-cost sharing is reduced, or the year’s end, which starts the reimbursement cycle anew.

CV medications account for a quarter of Medicare Part D spending and more than a third of drug volume, they wrote, adding that some evidence suggests the improved access to these drugs under Medicare Part D has helped decreased CV-related morbidity and mortality. While some studies have documented an increase of drug discontinuation when beneficiaries reach the donut hole, none has specifically looked at CV conditions.

For their study, they looked at CV medication discontinuation, drug switching and the risk of CV-related death or hospitalization, comparing Medicare Part D enrollees who fell in the donut hole and were responsible for 100 percent of their drug costs (exposed) with those who fell in the coverage gap but received financial assistance (unexposed).

“Although the 2010 [Patient Protection and] Affordable Care Act contains provisions that will gradually eliminate the coverage gap over the next decade, there are no short-term solutions to closing the gap, and recent Congressional budget proposals aim to repeal these reforms,” Polinski and colleagues wrote. “Our study provides evidence about the effect of the coverage gap, as initially implemented, on beneficiaries with cardiovascular conditions and serves as a baseline by which any reforms may be judged.”

By linking prescription and medical claims data, they identified 122,255 Medicare beneficiaries with CV conditions who fell in the donut hole in 2006 or 2007. Those beneficiaries were followed until they experienced an event (death or hospitalization), reached the catastrophic coverage spending threshold, or year’s end.

For their analyses, they matched 3,980 exposed beneficiaries and 3,980 unexposed beneficiaries using propensity score and high-dimensional propensity score approaches. They then compared rates of CV drug discontinuation, drug switching and death or hospitalization for acute coronary syndrome plus revascularization, congestive heart failure or atrial fibrillation.

Polinski and colleagues found that exposed beneficiaries were 57 percent more likely to discontinue medication use. Exposed beneficiaries were more likely to discontinue beta-blocker use and statin use than were unexposed beneficiaries.

They calculated that approximately 2.9 million Part D beneficiaries discontinued drugs during an average period of 3.6 months while in the donut hole. But exposed beneficiaries were no more likely to switch CV drugs, die or be hospitalized than unexposed beneficiaries.   

Those results run counter to previous research findings that showed higher rates of death or hospitalization in Medicare Part D beneficiaries facing caps who discontinue drug use, the authors acknowledged. They attributed the difference to their shorter follow-up period.

“While most comparator studies in other settings had follow-up of one year or more, in our study, beneficiaries spent a median 119 days in the coverage gap follow-up period,” they explained. “Beneficiaries in our study also experienced a relatively small number of adverse events, limiting our power to detect differences between the exposed and unexposed groups.”

Despite using a number of approaches to adjust for confounding, they wrote that they cannot rule out unmeasured confounding in their study. They noted that 94 percent of beneficiaries were censored after entering a new benefit year, making long-term analyses beyond the scope of the study.

They wrote that their study demonstrated that “blunt cost-sharing mechanisms” such as the coverage gap may derail the benefits from efforts such as Medicare Part D by prompting elderly people with CV conditions to stop taking prescribed drugs.

“Given the results we observed, policymakers should be sensitive to the deleterious effects of the coverage gap on cardiovascular drug discontinuation and work to protect beneficiaries with CV conditions who may be vulnerable to it,” they concluded.