Impact of Statin Copayments on Adherence and Medical Care Utilization and Expenditures

Published Online: December 15, 2006
Teresa B. Gibson, PhD; Tami L. Mark, PhD, MBA; Kirsten Axelsen, MS; Onur Baser, PhD; Dale A. Rublee, PhD; and Kimberly A. McGuigan, PhD, MBA

Objective: To examine the effects of statin cost-sharing (ie, copayments, coinsurance) on adherence to statin medications and the impact of adherence on healthcare utilization and spending.

Study Design: Retrospective, observational study of statin users receiving health benefits or supplemental coverage from employer-sponsored health plans.

Methods: Medical and pharmacy claims were selected from the Medstat MarketScan database for patients who were continuously enrolled from 2000 through 2003. Two-stage residual inclusion models were estimated. The first stage modeled adherence to statins, which was derived from the medication possession ratio, and represented the percentage of days on therapy in an 18- month time frame, July 2001 through December 2002. In the second stage, generalized linear models were used to estimate 2003 utilization and expenditures. Separate estimates were produced for new statin users (n = 24 113) and continuing statin users (n = 93 253).

Results: Lower statin copayments were associated with higher levels of statin adherence. In percentage terms, when holding all other variables at their mean value, a $10 increase in copayment resulted in a 1.8 percentage point reduction in the probability of adherence for new users and a 3 percentage point reduction in the probability of adherence for continuing users. For continuing users adherent to statins, total costs did not change, but fewer negative events (emergency department visits, hospitalizations, and coronary heart disease-related hospitalizations) occurred.

Conclusions: Policy makers and plan managers should consider interventions that improve adherence to statins, such as lower copayments.

(Am J Manag Care. 2006;12:SP11-SP19)


The direct medical costs and indirect costs due to lost productivity from coronary heart disease (CHD) in the United States are estimated to exceed $142 billion in 2006.1 One of the primary risk factors for CHD is high blood cholesterol, and more than 130 million adults in the United States have borderline-high or high total blood cholesterol levels.2 In addition, more than 30% of American adults have high low-density lipoprotein cholesterol (LDL-C) levels, undesirable cholesterol that is associated with a higher risk of CHD.

The 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase inhibitors (statins) are a well-accepted medical treatment that reduce LDL blood cholesterol levels. Evidence from clinical trials such as the Scandinavian Simvastatin Survival Study,3 the Long-Term Intervention with Pravastatin in Ischaemic Disease study,4 the West of Scotland Coronary Prevention Study,5 and the Air Force/Texas Coronary Atherosclerosis Prevention Study6 reveal that adherence to statin medications is associated with lower cholesterol levels and lower levels of CHD morbidity and mortality.3-7 These studies also reveal that the clinical benefits of statin use increase with the amount of time on statin therapy.3-6 Even so, adherence to statin medications is typically low,8,9 with adherence rates rapidly declining initially and continuing to decline throughout the first few years after initiation of statin therapy.8,10

Adherence to statin medications has been determined to be related to a variety of factors including sociodemographic characteristics, CHD risk, and comorbidities.8,11-15 Recent evidence has demonstrated that patient financial incentives (ie, copayments, coinsurance) also affect statin adherence.12-15 As statin cost-sharing levels increase, adherence to statins falls. Patient cost-sharing also has been demonstrated to be a financial barrier to the utilization of other classes of medication that are typically used to treat chronic disease.16,17 However, the relationship between cost-sharing and adherence to medications has not been consistent across all medication classes.16

Prescription drug cost-sharing levels (ie, copayments, coinsurance) for enrollees in employer-based health plans have increased steadily over time.18 In addition, prescription drug cost-sharing trends show that copayments and coinsurance are still rising. In a recent Kaiser Family Foundation/Health Research and Educational Trust survey of employer-sponsored health benefits, almost half of the firms (45%) responded that they were very or somewhat likely to increase cost-sharing for prescription drugs in the next year.18

In this study we first analyzed the relationship between statin cost-sharing levels and adherence to statin medications. Then, we analyzed the relationship between statin adherence and healthcare utilization and expenditures. This study extends our previous research, which used a panel data framework to examine the relationship between monthly statin cost-sharing and monthly statin adherence.13 In this study we used a patient-level model linking cost-sharing to adherence. Then, unlike our previous study, we examined the association between adherence and healthcare utilization and spending. To our knowledge, no study has concurrently examined the relationship between statin cost-sharing, adherence, and healthcare utilization/spending.

Several previous studies focused on the relationship between cost-sharing and adherence to statins.12-15,19 These studies show that there are at least modest declines in statin adherence as statin copayments rise. For example, doubling copayments from $10 to $20 led to a drop in annual compliance of 6 to 10 percentage points for all cholesterol-lowering therapies.14

Two studies examined the relationship between cost-sharing and measures of healthcare utilization or outcomes. In the first study, Schultz and colleagues examined the healthcare experience of 21 229 new statin users who were enrolled in 23 fee-for-service independent practice association health plans and who were also at high risk for CHD.15 Although adherence to statin therapy in the first 90 days after initiation of therapy was positively associated with reaching target levels of LDL-C, the average statin copayment, which was measured during the same time period, was not associated with LDL-C goal attainment.

Perhaps the most comprehensive analysis so far was reported by Goldman and colleagues, who studied the healthcare experience of 62 744 adults with employer-sponsored health benefits in 88 health plans who initiated cholesterol-lowering therapy.14 The authors reported that higher levels of cost-sharing were associated with a reduction in compliance with cholesterol-lowering therapy. The authors also found that compliance with cholesterol- lowering therapy (medication possession ratio [MPR] ≥ 80%) in the past (up to 4 years of experience were measured) was associated with a reduction in the annual rate of hospitalization (all cause and circulatory) and in emergency department (ED) visits (all cause and circulatory). Although Goldman and colleagues estimated the financial effects of changes in copayment levels based on the changes in utilization, the impact of variations in cost-sharing on actual spending was not examined.

Finally, 1 study analyzed the relationship between adherence and utilization and spending, but did not examine the effects of cost-sharing. In this study of 2981 privately insured patients diagnosed with and treated for high cholesterol, Sokol and colleagues found that as adherence to cholesterol-lowering medications rose, medical costs declined and the annual risk of hospitalization decreased.20 As adherence rose, prescription drug spending also rose and total costs (prescription drug and medical) declined, although neither of these relationships were statistically significant.

Our article adds to the literature in several ways. First, we studied the relationships among copayments, adherence, and utilization/spending within a single study, which to our knowledge is a more comprehensive approach than has been used in the past. Second, we measured actual, not imputed, utilization and expenditures to determine the effects on direct medical costs and utilization patterns. Third, separate estimates were produced for 2 distinct groups of statin users, new (statin naïve) users and continuing users, whereas other studies focused on new users or combined all types of statin users. Finally, we used 2-stage residual inclusion models to estimate these relationships and produce consistent estimates in the nonlinear utilization and spending models.

METHODS

This study was based on data from the 2000-2003 Medstat MarketScan database, which represents the healthcare experience of at least 6 million enrollees with employer-sponsored health insurance each year. The database also includes Medicare-eligible retirees with employer-sponsored supplemental medical benefits and reflects Medicare utilization in addition to the employer-sponsored portion. Medical and prescription drug claims were linked to patient enrollment information to create the analytic dataset.

A retrospective study was conducted among statin users who were aged 18 years or older and did not have an indication of pregnancy (which can affect prescription drug use) during the study time frame. Patients also were continuously enrolled from 2000 through 2003. Because statin utilization patterns can differ markedly between incident users of statins and prevalent users of statins,13 patients were categorized into 2 groups: (1) new/incident statin users whose initial statin prescription occurred in the first 6 months of 2001 and who had no statin prescription fills in the prior year (n = 24 113), and (2) continuing/prevalent statin users who had a first observed prescription fill in 2000 and also had at least 1 statin fill during the study time frame (n = 93 253).

Analytic Framework

We analyzed the relationship between statin cost-sharing, adherence, and utilization/spending by first estimating the relationship between copayments and adherence to statin medications (controlling for covariates) during an 18-month time frame, which was July 2001 through December 2002. Statin adherence was measured over the 18-month time period to assess adherence behavior over time. We then estimated the relationship between statin adherence and utilization/spending (controlling for covariates) in the subsequent year, 2003. This framework allowed examination of the relationship between statin cost-sharing and utilization/spending primarily through the mechanism of adherence to statin medications.

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