A review of the most compelling papers linking better medication adherence with better clinical outcomes
By Katrina Firlik, MD
Co-Founder and Chief Medical Officer
We know that for a multitude of chronic diseases, prescription medications are key to controlling disease progression, preventing complications, and improving outcomes. And we know that medications work best when taken on a regular basis. Medication adherence is, therefore, a requirement to maximizing outcomes.
Although the link between adherence and outcomes is already well understood, ongoing evidence in the form of clinical studies can serve as further motivation to expand adherence efforts by payers, pharmaceutical companies, and other healthcare constituencies.
Improving medication adherence represents a win-win for all.
- For patients and their families: better outcomes and quality of life.
- For payers: lower costs and improved member health.
- For pharmaceutical companies: greater drug efficacy and a return on investment.
- For hospitals and physicians: fewer readmissions, greater satisfaction, and higher ratings.
And, although we intuitively understand the link between adherence and outcomes, elucidating this link across conditions and patient demographics with greater granularity can be instructive, particularly in targeting the right patients for adherence interventions.
Here we summarize the top studies that, in our opinion, best exemplify the link between better medication adherence and better clinical outcomes. Outcomes are measured not only by health-related events (hospitalizations, emergency room visits) but also, in obvious lockstep, by healthcare spend.
Given the multivariate factors beyond medication adherence that can impact outcomes—including socioeconomic and behavioral factors—retrospective studies must always be judged in light of their inherent limitations. However, the most sophisticated studies at least attempt to control for these common variables.
Our hope is that a greater understanding of the role that medication adherence plays in both individual and population health, via high-quality quantitative analyses, will help place a stronger emphasis on the need for compelling and effective adherence interventions.
Anti-hypertensive medications and cardiovascular outcomes
This paper is a meta-analysis of 16 previously published studies that covers over 2.7 million patients. Their key findings were the following:
- There was a linear, direct, relationship between better adherence to anti-hypertensive medications and fewer cardiovascular events, and
- In stratifying adherence groups, for every 20% increase in adherence, the risk of a cardiovascular-related event was 13% lower.
Statin adherence linked to better outcomes and lower healthcare spending
In this study of over 77,000 Medicare supplemental beneficiaries, adherence was defined as a PDC (proportion of days covered) of > 80%. Patients who were adherent were twice as likely to achieve control of their cholesterol levels and demonstrated nearly 15% lower total healthcare costs over the course of one year. This amounted to an average of $157 less spend per adherent member per month as compared to a non-adherent member.
Targeting patients with 3 more comorbidities, as well as already-adherent patients
This study evaluated the link between medication adherence and healthcare spend in over 800,000 commercially insured patients with a range of comorbidities over the course of two years. Adherence was defined as an MPR (medication possession ratio) of > 0.8. The change in healthcare spend was assessed not only for patients who moved from the “non-adherent” to the “adherent” category, but also for those who moved in the opposite direction. Interestingly, the increased costs incurred by a patient who moved from “adherent” to “non-adherent” was greater than the savings demonstrated by a patient who became adherent.
This makes a compelling argument to target not only non-adherent patients for an adherence intervention, but also the already adherent in order to keep them on track. Furthermore, patients with 3 or more comorbidities were found to be the best targets for intervention, as they demonstrated up to a 7 times greater difference in spend as compared to patients with fewer comorbidities.
Medication adherence is associated with lower costs across four common conditions
In this study by CVS Caremark of over 135,000 patients across four common conditions—diabetes, hypertension, dyslipidemia, and congestive heart failure—adherent patients cost less than non-adherent patients, despite the increased drug costs associated with greater adherence. The annual savings were as follows: $1,860 in dyslipidemia, $4,337 in hypertension, $4,413 in diabetes, and $8,881 in congestive heart failure. This decrease in cost was driven primarily by fewer emergency room visits and inpatient hospital stays.
The cost of medication nonadherence in Medicare
Perhaps the largest study to date, over 14 million patients on Medicare were assessed, focusing on the four vascular-related chronic conditions commonly assessed in adherence studies: diabetes, hypertension, dyslipidemia and congestive heart failure. Their findings were most striking for patients with hypertension: “If the 25% of beneficiaries with hypertension who were nonadherent became adherent, Medicare could save $13.7 billion annually, with over 100,000 emergency department visits and 7 million inpatient hospital days that could be averted.” Clearly, better adherence represents a serious win-win for all constituents, including patients and payers and, when that payer is the US government, potentially taxpayers as well.