Medication Adherence and Enrollment in a Consumer-Driven Health Plan

Medication adherence was lower for some drug classes among CDHP patients who enrolled in consumer-driven health plans compared with patients who continuously enrolled in traditional managed care plans.

Published Online: February 01, 2010
Song Chen, MS; Regina A. Levin, MPH; and James A. Gartner, RPh, MBA

Objective: To evaluate the impact of enrolling in a consumer-driven health plan (CDHP) on adherence to maintenance drugs.

Study Design: Two-year retrospective cohort study.

Methods: Consumer-driven health plan patients were enrolled in a traditional managed care plan in 2005 (pre-year) and a full-replacement CDHP in 2006 (post-year). Traditional-plan patients voluntarily enrolled in a traditional plan in both years. Adherence measures included (1) post-year continuation rate among continuous users, (2) time to refill the first prescription in the post-year, (3) change in the compliance rate from the pre- to the post-year, and (4) total days with continuous drug supply in the post-year. Analysis was conducted on 8 drug classes.

Results: The CDHP patients had a slightly higher illness burden and used more medication in the pre-year. The continuation rate was relatively high for all drug classes, although the CDHP cohort had a lower probability of continuing cardiac and cholesterol drugs. Consumer-driven health plan patients took slightly longer on average to refill their first prescription in the post-year for cardiac, hypertension, cholesterol, and thyroid drugs. The compliance rate dropped over time in both cohorts, but the reduction was bigger among CDHP patients for 3 drug classes (adjusted ratio of the odds ratios was 0.77, 0.78, and 0.69 for asthma, cardiac, and cholesterol drugs, respectively). The CDHP patients also terminated their continuous drug supply 21 days earlier for epilepsy drugs and 27 days earlier for cholesterol drugs.

Conclusions: Adherence was lower for a few drug classes among CDHP patients.

(Am J Manag Care. 2010;16(2):e43-e50)

The impact on adherence to maintenance drugs of enrollment in a consumer-driven health plan (CDHP) was assessed in a 2-year retrospective cohort study.

  • The compliance rate dropped over time in both the CDHP and traditional managed care cohorts, but the reduction was bigger among CDHP patients for asthma, cardiac, and cholesterol drugs.
  • The CDHP patients also terminated their continuous drug 21 days earlier for epilepsy drugs and 27 days earlier for cholesterol drugs.
Poor adherence to drug regimens is a costly problem. It increases the risk for negative health outcomes as well as increased healthcare costs.1-3 Yet nonadherence is common; approximately 40% to 60% of patients do not take medications as prescribed.4-10 High-deductible health plans have the potential to discourage drug adherence by placing additional financial burdens on members. In these plans, members may face larger out-of-pocket expenses at the beginning of the plan year in the form of higher deductibles, which could contribute to delays in refilling prescriptions or stopping medication altogether. Using enrollment and claims data from a national insurer, this retrospective cohort study tested whether patients who enrolled in a consumer-driven health plan (CDHP) that fully replaced a traditional plan became less adherent to medications for chronic conditions compared with those who were continuously enrolled in a traditional managed care plan.


During the past 5 years, CDHPs have experienced fast growth. It has been estimated that in 2008 there were 10 million to 12 million CDHP enrollees nationally.11 The study insurer’s CDHP membership was about 750,000 in 2005. Membership almost doubled in 2006 and exceeded 3 million in 2009. Initially a CDHP was most commonly offered as an option alongside traditional plans, but recently an increasing number of employers have fully replaced their traditional plans with CDHPs. This insurer experienced a 67% increase between 2006 and 2008 in the number of employers that offered full-replacement CDHPs. Only fullreplacement CDHPs were used in this study to eliminate the selection bias that might have occurred with optional CDHPs.

Consumer-driven health plans typically consist of a personal care account and a deductible (usually $3000-$4000). Under a basic CDHP model, members receive an annual allocation of money into an account and can use this money to pay for medical and pharmacy services. Unused funds can be rolled over to the next year and be added to the next year’s fund deposit. Once the account is exhausted, members are financially responsible for the medical and pharmacy services until a deductible is met. After the deductible is met, members are partially financially responsible for the services until the annual out-ofpocket maximum is met. There are 2 types of accounts: health reimbursement accounts (HRAs) and health savings accounts (HSAs). The primary differences are that (1) both the employer and the member can contribute to the HSA, whereas only the employer can contribute to the HRA; and (2) the employee owns the HSA, whereas the employer owns the HRA (ie, after discontinuing employment, the employee loses the money in the HRA account). The HRA and the HSA have had roughly equal market penetration in recent years.11

Prescription drugs are paid for differently in CDHPs than in traditional managed care plans. In CDHPs, members pay the full amount for which the insurer has contracted with the pharmacy until members have satisfied the deductible. Once the deductible is satisfied, members are responsible for a copayment. In traditional managed care plans, members are responsible for prescription copayments regardless of whether the deductible is satisfied. (In some cases plans will have separate deductibles for the pharmacy benefit.) Typically, traditional plans use a tiered pharmacy design with different copayment tiers for brand versus generic drugs.

At the time this study was conducted, research on medication adherence in CDHPs was limited and the results were mixed. Some researchers reported increased use of maintenance medications and decreased pharmaceutical expenditures among CDHP enrollees.12 Some researchers reported that CDHP enrollees and traditional-plan enrollees had similar rates of brand utilization,13 generic utilization,14 and medication adherence.14,15 Yet other studies found that CDHP members tended to use fewer prescription drugs,16 were less compliant with drug  regimens,17,18 were more likely to discontinue chronic illness medications,14 and were more likely to skimp on needed medications because of cost.19 These studies have limited generalizability with respect to medication adherence because they examined the experience of only 1 or 2 employers, they measured general medication utilization rather than adherence, or they looked at cross-sectional differences without controlling for baseline differences.


Setting and Design

The study insurer substantially increased membership in CDHP in 2006. The number of contracted employers increased by 300% to 14,500 and the total number of enrollees doubled to 1.5 million. That year 55% of the employers fully replaced the traditional plan with a CDHP. These full-replacement employers represented 35% of the new member population.

This retrospective cohort study identified a CDHP cohort from 33 employers and a traditionalplan cohort from 47 employers. All employers were middle to large size (≥100 employees). These employers offered traditional plans that had been provided by the same insurer in 2005 and started offering CDHPs to employees in 2006. Both self-insured and fully insured employers were included. Employers in the CDHP cohort offered CDHP as the only choice (full-replacement plan), whereas those in the traditional-plan cohort offered a traditional plan as an option in addition to a CDHP. The traditional plans included preferred provider organization, point-of-service, and exclusive provider organization plans. The CDHPs included HRAs and HSAs. Preliminary examination of the data showed that HSA and HRA members had similar adherence patterns. The HRA and HSA members were combined in the CDHP cohort; they will be analyzed separately in a subsequent study. Tiered pharmacy designs were used in all traditional plans.

Study Subjects

The unit of analysis is per patient per drug class. Patients were eligible for the CDHP cohort if they enrolled in a traditional managed care plan in 2005 (pre-year) and a fullreplacement CDHP in 2006 (post-year). Those who were eligible for the traditional-plan cohort voluntarily enrolled in a traditional plan in 2005 and 2006. Other inclusion criteria included continuous enrollment, under age 64 years on the last day of the 24-month study frame between January 1, 2005, and December 31, 2006, both pharmacy and medical benefit coverage, and no other source of health insurance. (All but 2 employers had January-start coverage, for whom the study frame was from January 1, 2005, to December 31, 2006. The study frame for the 2 non–January-start employers also was 24 months but was shifted to the applicable starting month.) Patients who used insurance from another carrier were excluded from this study due to the unavailability of insurance claims.

For a given drug class, a patient was identified if he or she had at least 1 prescription in that drug class during the first quarter of the pre-year and at least 1 refill during the last quarter of the pre-year. Those who did not have a script in the preyear were excluded from the analysis due to the unavailability of baseline prescribing experience. Eight therapeutic classes for conditions including asthma, cardiac, diabetes, epilepsy, hypertension, cholesterol, rheumatoid arthritis, and thyroid were selected because the drugs in these classes are rarely used to treat other conditions and should be taken continuously. Patients were allowed to switch drugs as long as they continued with a drug in the same class. Specified Therapeutic Class code, a drug classification system developed by the First DataBank, was used to define drug classes. Study subjects who had prescriptions in multiple drug classes were treated as separate individuals.

Risk Assessment

Using enrollment data and medical and pharmacy claims, patients’ health risk scores in the pre-year were computed and used in multivariate modeling. Health risk score measures the relative resources that are expected to be required for healthcare. Health risk was assessed with Episode Risk Groups, a derivative work based on Episode Treatment Group methodology, a widely used software product for illness classification and episode building (a product of Ingenix, a subsidiary of UnitedHealth Group). The literature reports that Episode Risk Group scores highly correlate with other risk-adjusted measures of practice efficiency such as Adjusted Clinical Groups, Burden of Illness Score, Clinical Complexity Index, Diagnostic Cost Groups, and General Diagnostic Groups.20

Outcome Measures

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