The American Journal of Managed Care July 2009
Impact of Workplace Health Services on Adherence to Chronic Medications
Patients who used workplace primary care and pharmacy services had higher adherence rates to medications for their chronic conditions than community-treated patients.
Objective: To test the association between integrated workplace health and pharmacy care and medication adherence.
Study Design: Adherence rates for commonly used chronic disease medications were compared in a retrospective, non–case-controlled study of 4476 workplace-treated patients versus 13,134 community-treated patients.
Methods: Pharmacy claims data were used to compute the medication possession ratio for patients who received care in different settings for 20 therapeutic classes. Statistical tests for assessing between-group differences were performed, controlling for differences due to age, sex, number of chronic conditions, number of medication therapeutic classes, and patient out-of-pocket cost per therapy day. Results were reported for overall adherence as well as adherence for patients on
Results: Significant differences were found between workplace-treated patients and community-treated patients. Workplace-treated patients had overall adherence rates that were 9.72% higher than those of community-treated patients. This pattern was repeated with an overall adherence rate that was 9.52% higher for workplacetreated patients when prescriptions were limited to medication new starts.
Conclusions: Integrated workplace primary care and pharmacy services are one way to increase medication adherence. These services have the potential not only to save healthcare dollars, but also improve the lives of chronically ill patients.
(Am J Manag Care. 2009;15(7):e53-e59)
The association between integrated workplace health and pharmacy care and medication adherence was examined in a retrospective study of workplace-treated patients versus community-treated patients.
- Patients who used workplace primary care and pharmacy services had higher adherence rates to medications for their chronic conditions.
- There was a significant trend regardless of the medication type, number of days supply, or geographic location toward workplace-treated patients being more adherent to drug treatment.
- By investing in integrated workplace primary care and pharmacy services, employers may realize improved medication adherence rates, resulting in potential healthcare cost savings.
Many factors have been demonstrated to play a role in medication adherence. Prescription-related issues include dosing frequency and prescription duration. Patient out-of-pocket costs are now well established as an important contributor, with increasing costs associated with lower medication adherence. Other patient-related issues include age, sex, health status, and comorbidities.6,7 Additionally, adherence is generally greater for medications that provide symptom relief, as opposed to those used for treatment of a generally asymptomatic condition.8
An important factor in medication adherence appears to be patient understanding and awareness of the condition being treated.9 With healthcare providers often ill equipped to address low health literacy in terms of training, time, and resources, this issue represents an ongoing and significant concern.
As employers become more involved in efforts to improve healthcare quality and control medical expenditures, maximizing medication adherence rates represents an important opportunity. Value-based benefit design strategies, such as lowering copayments for medications used to treat chronic conditions, represent one successful approach used by a number of employers.10
Some employers have opted for a more comprehensive approach to healthcare management by direct contracting for workplace primary care and pharmacy services. As a result of improved access to care and elimination of the traditional fee-for-service model, patients can benefit from far more clinician contact time for more effective health education and management. This approach to healthcare delivery is likely to result in enhanced patient understanding and self-care of chronic conditions, including medication adherence. Yet despite the fact these employer-sponsored offerings have existed for decades, no studies to our knowledge have been published that demonstrate an association between workplace health services and medication adherence. Other studies have considered the impact of integrated workplace health services on disease management11 and antibiotic prescribing,12 with promising results. We hypothesize that this integration will have a similar influence on medication adherence.
The objective of this study was to test the hypothesis that patients who use an integrated workplace primary care and pharmacy service have higher rates of adherence to commonly used medications for chronic conditions than patients who use community-based services. This retrospective, non–case-controlled study compared the medication adherence of these 2 groups during 2006.
The health benefit–covered population from 8 different locations of a large, self-insured employer’s active and retiree population along with their eligible dependents was selected for potential inclusion in this study. Demographic, medical claims, and pharmacy claims data were obtained for this population covering all dates of service during the time period of January 1, 2005, through December 31, 2006. All locations had stable populations covered by the same health benefit plan, and the 4 workplace health center locations have been continuously operated by the same workplace health vendor for more than 15 years. Calendar year 2005 was used as the baseline year from which the populations were selected into their respective groups, and calendar year 2006 was the study year from which medication adherence was determined using the methods described below.
First, from the baseline year (2005) all covered lives with a claim for at least 1 medical office visit and 1 or more prescriptions were selected. The requirement of an office visit provided the opportunity for a physician to discuss compliance with drug therapy with the patient. At the 4 locations where the
population had access to workplace primary care and pharmacy (called workplace health centers from this point forward), only those patients who had at least 1 office visit at the workplace health center and at least 1 prescription filled at the workplace pharmacy were selected as the main focus of this study (from this point on called the workplace-treated group). The individuals at these locations who used community health services only were excluded to
reduce selection bias, as those who had access to workplace health services but chose not to use them may differ from those who used workplace health services. The comparison group (from this point on called the community-treated group) was selected from the remaining 4 locations without workplace health centers, as long as they met the minimum office visit and prescription requirements.
Next, for both groups, pharmacy claims data were used to associate the National Drug Code for each prescription filled with the appropriate American Hospital Formulary Service number to identify the therapeutic class for that drug.13 The top 20 therapeutic classes of drugs used primarily to treat chronic conditions for this population were then identified based on the number of prescriptions filled and the number of unique patients with prescriptions in each class. Therapeutic drug classes used to treat diabetes mellitus, hypertension, heart arrhythmia, heart disease, and thyroid disease were included. Finally, only patients with at least 1 prescription in 2006 for 1 or more drugs within these 20 therapeutic classes were retained for analysis.
The final study population consisted of 17,610 unique patients who were on average 60 years of age. More than half of the study population was male, and 61.95% were retirees or retiree dependents. To assess the level of chronic disease burden in this population, we reviewed the diagnosis codes for each patient from the medical claims data and determined the prevalence of relevant conditions for the therapeutic classes included in the study. The average number of unique therapeutic classes for which each person had prescriptions filled also were determined using all possible therapeutic classes (not limited to the top 20), with a mean of 5.8 classes. Patient out-of-pocket costs for prescription drugs varied by drug tier, days supply, and where the prescription was filled. Because decreased adherence has been linked to increases in copayments14 and the average copayment amount differed by group, we computed cost per therapy day and controlled for this in the analysis. As shown in Table 1, the average patient cost per therapy day was $0.45.
Workplace-treated patients (n = 4476) were 4 years older than community-treated patients (n = 13,134), and more likely to be male and retired. The workplace-treated group alsohad, on average, a higher chronic disease burden and were prescribed a slightly higher number of therapeutic classes than the community-treated group. Patient cost per therapy day was lower for the workplace-treated group ($0.29 vs $0.50). Because the differences in age, sex, number of chronic conditions, number of therapeutic classes, and the patient out-of-pocket cost per therapy day were statistically significant at the
P <.05 level, we controlled for them in the analysis.
Our measure of adherence was based on the medication possession ratio (MPR). This is defined as the proportion of days covered by a given drug class over the course of the year, based on the number of days supplied and the quantity of medication dispensed for each filled prescription.15 We therefore defined actual adherent days as the number of days in 2006 that the patient had the medicine available from the date of service of the first prescription for each therapeutic class either through December 31, 2006, or to the termination of patient eligibility for benefits, whichever came first. Potential adherent days were defined as the number of days in 2006 from the date of service of the first prescription for each therapeutic class either through December 31, 2006, or to the termination of patient eligibility for benefits, whichever came first. Thus, the MPR was calculated as:
MPR = Actual Adherent Days ÷ Potential Adherent Days
A day was assumed to be covered if any drug in that class was available. Because of this, estimates of adherence represent an upper bound on actual adherence with prescribed therapy. Although this measure may not be as accurate as pill counts or similar methods involving direct measurement, MPR both is routinely used as a measure of adherence in the medical literature7,10,16 and is a recommended measure of medication adherence for population-based outcomes evaluations by the DMAA: The Care Continuum Alliance in volume 3 of the Outcomes Guidelines Report published in 2009 and by the International Society of Pharmacoeconomics and Outcomes Research.17
It is worth noting that MPR is a medication-specific measurement, rather than a patient-specific measurement. Thus, patients taking different medications may have a different MPR for each of their medications. In this study we intentionally focused on adherence for patients at various points during their drug treatment. The literature on issues surrounding compliance with “new starts” of medication is well established, 7 so although new starts are addressed in the Results section, they are not the main focus of the study.
The χ2 and t tests were used for simple comparisons of differences between the groups for categorical and continuous variables, respectively. Linear regression was used to assess differences in medication adherence rates between the groups while controlling for age, sex, chronic conditions, number of therapeutic medication classes, and patient out-of-pocket cost per therapy day. For all statistical tests, a 2-tailed P value of <.01 was considered statistically significant. All statistical analyses were performed with SAS statistical software, version 9.1.3 (SAS Institute Inc, Cary, NC).
The workplace-treated group had higher adherence rates across all therapeutic classes than the community-treated group (Table 2). Two therapeutic classes for drugs used to treat heart arrhythmia, class 1B and 1C antiarrhythmics, did not meet the test for statistical significance at the P <.01 level. All other therapeutic classes showed statistically significant differences, with the largest difference found for class III antiarrhythmics, a 19.91% higher adherence rate forthe workplace-treated group. When therapeutic classes were combined into disease groups, medications used to treat diabetes showed the largest increase in adherence (12.65%) for the workplace-treated group. Smaller, but similar increases in adherence were seen for hypertension, heart arrhythmia, and heart disease. Across the 20 therapeutic classes, the MPR for the workplace-treated group was 9.72% higher than that for the community-treated group.