Adherence to statin therapy is known to be poor, estimated to be about 50% at 12 months after initiation, even among patients with good insurance benefits, said Sebastian Schneeweiss, MD, Associate Professor of Medicine and Epidemiology at Harvard Medical School in Boston, MA, during the American Heart Association 2008 Scientific Sessions.
Dr Schneeweiss presented results of a study that evaluated the consequences of copayment and coinsurance policies on the initiation of statin therapy after acute myocardial infarction (MI) and adherence to statin therapy in older individuals (age *65) residing in British Columbia (BC). In a population-based naturalistic study of older adults insured by the Canadian healthcare system, adherence to statin therapy was reduced by abrupt changes in health plan coverage, such as copay and coinsurance. At 15 months, adherence rates were approximately 5% lower for those with cost-sharing benefits compared with patients who were fully insured. Initiation of coinsurance almost doubled the risk of non-adherence to statin therapy.
"Although interventions such as copays and coinsurance may produce net savings for the health plan, in the long run they can lead to unanticipated harmful outcomes that increase costs," said Dr Schneeweiss, noting that a 100% coinsurance benefit under the Canadian system is similar to the so-called doughnut hole of Medicare Part D in the United States. "Many, but not all, commercial drug benefit plans under Part D have chosen to close the doughnut hole," he added.
The study population was drawn from the BC-funded drug insurance plan and included 3 cohorts of elderly patients:
- Group 1 (n = 12,500) was the baseline cohort, with full prescription drug coverage within 6 months before January 2001
- Group 2 (n = 13,186), a cohort that started statin therapy within 6 months before January 2002, when a $25 copay policy was initiated
- Group 3 (n = 15,830), a cohort initiating statins within 6 months before May 2003, when a policy of 25% cost-sharing of drugs was put into effect.
Follow-up for each cohort began on policy initiation date and extended for 9 months after policy changes.
A group of Pennsylvania (PA)-based Medicare recipients who were hospitalized for acute MI and had full drug coverage (no copayments) throughout the study served as a time-trend control group.
The number of new statin users grew 4 to 8 times faster compared with the population growth of BC residents aged *65 years. Over time, an increased number of older patients and patients with cardiac risk factors were using statins.
Adherence—defined as more than 80% of proportion of days covered—was calculated for each patient each month. Median patient cost-sharing for a 90-day statin supply was $21.50 (Canadian) under the copay policy and $41.80 (Canadian) under the coinsurance policy. At 6 months after initiating statin therapy, adherence rates for cohorts 1, 2, and 3 were 73.2%, 74.5%, and 72%, respectively. At 15 months, adherence rates fell to 55.8%, 50.5%, and 50.8%, respectively.
When looking at a subgroup of post-MI patients in this study, no copay effect was evident with regard to statin therapy initiation. The PA-based control group had lower levels of statin use than the BC cohort, which could be partly explained by the patients' poor health and low-income status. Lower income was associated with an increased likelihood of stopping statin therapy independent of insurance status. Taking statins for secondary prevention after acute MI or revascularization decreased the odds of stopping statin use by 37%. Independent of insurance status, a recent history of MI, revascularization, or multiple comorbidities made patients less likely to discontinue statin therapy.