Blood Pressure Control Among Adherent vs Nonadherent Medicare Patients With Hypertension

ABSTRACT

Objectives: Medication adherence measures for hypertension drive financial incentives and patient care strategies for many value-based health care programs. The association between medication adherence and hypertension control as a value-based quality measure is not well described. The objectives of this study were to compare blood pressure (BP) control among Medicare and Medicare Advantage patients who meet vs do not meet the medication adherence for hypertension (MAH) measure and compare patient and prescription factors associated with adherence vs disease control.

Study Design: Retrospective cohort study using linked payer and electronic health record data from a single health system.

Methods: Medicare patients eligible for MAH in 2023 were categorized as adherent or nonadherent according to measure specifications, and hypertension control was defined as a primary care office BP less than 140/90 mm Hg or less than 130/80 mm Hg. Multivariable logistic regression was used to identify factors independently associated with adherence and disease control.

Results: Of the 5206 patients evaluated, 77.9% were classified as adherent to the MAH measure. Of adherent patients, 77.2% achieved a BP less than 140/90 mm Hg vs 73.5% of nonadherent patients (P = .01), and 45.9% and 43.4%, respectively, achieved a BP of less than 130/80 mm Hg (P = .14). White race and younger age were positively associated with hypertension control, whereas extended days’ supply and non-White race were associated with meeting the MAH measure.

Conclusions: Patients classified as adherent were more likely to achieve a BP less than 140/90 mm Hg, but achievement of BP less than 130/80 mm Hg did not differ between groups. A sizeable proportion of patients who did not meet the adherence measure (73.5%) achieved a BP less than 140/90 mm Hg. Factors associated with adherence vs disease control differed. Emphasis on disease control over medication adherence measures may more meaningfully reflect high-value clinical care.

Am J Manag Care. 2026;32(7):In Press

Takeaway Points

• Many patients who do not meet adherence metrics still have well-controlled blood pressure.
• Current adherence measures may misrepresent provider performance and
  patient outcomes.
• Shifting focus to actual blood pressure control could better guide quality improvement and payment strategies.
• Employers and policy makers may consider outcome-based metrics to better assess value and care effectiveness.

Medication adherence measures based on a dichotomized value of the proportion of days covered (PDC) calculated using claims data are triple weighted in Medicare Advantage quality programs and are utilized for some commercial health plans. The clinical importance of adherence to medications for chronic conditions such as hypertension is undisputed.^1-3 Large observational studies have linked poorer hypertension adherence measure performance to higher health care costs^4,5 and, in the case of statins, to poorer hyperlipidemia control and higher mortality.⁶ However, the retrospective observational designs of these studies limit their ability to control for potential confounders such as patient socioeconomic status and potential coding errors, which may lead to misclassification for eligibility for the adherence measures.⁷

Shortcomings of adherence measures have been highlighted in the literature. Reliance on refill gaps alone to calculate adherence is inherently flawed. This technique does not account for medically justified gaps (eg, medication intolerance leading to medication changes or discontinuation, hospitalizations) or other factors (eg, prior authorization requirements or medication fills made outside the patient’s pharmacy benefit) that could potentially lead to an underestimation of true adherence.^8,9 A 2020 analysis identified common pitfalls associated with adherence measures based on refill patterns. The authors concluded that adherence values are easily skewed by slight differences in definition and may lead to false conclusions about adherence.¹⁰ Another limitation of the PDC is that it only measures whether the patient had the medication dispensed, which does not guarantee the patient administered or ingested it as prescribed.⁸ A large data-based study found patients above the PDC threshold of 0.8 had slightly higher blood pressure (BP) control rates, but a substantial proportion of patients classified as nonadherent also had controlled BP.¹¹

This quality improvement evaluation aimed to assess the relationship between performance on the medication adherence for hypertension (MAH) measure and BP control among Medicare and Medicare Advantage patients and identify factors associated with meeting the adherence measure vs achieving BP control.

METHODS

Study Design

This retrospective, observational cohort evaluation of Medicare and Medicare Advantage patients who were included in or would be eligible for the MAH measure in 2023 assessed the relationship between BP control and medication adherence for select antihypertensive medications. This evaluation utilized data from a single-center health system in Colorado, combining payer-reported MAH data with linked electronic health record (EHR) information. This study was deemed exempt from review by the Colorado Multiple Institutional Review Board.

Population

Included patients were 18 years or older, had Medicare or Medicare Advantage plans, were eligible for the MAH measure in 2023, and had a primary care BP measurement in 2023. Medicare Advantage patients were identified using payer-provided reports in which MAH eligibility had already been established, and Medicare patients were identified using prescription claims data and applying MAH eligibility criteria based on claims data plus the EHR. Primary care BP measurements were obtained through the EHR. Eligibility for MAH is defined as 2 or more prescription claims during the measurement year for a renin-angiotensin-aldosterone system (RAAS) antagonist medication. Patients in hospice, with end-stage renal disease, or who took sacubitril/valsartan were excluded.¹² Adherence was measured using PDC, based on the fill dates and days’ supply for each prescription fill. The denominator for the PDC is the number of days between the first fill of the medication during the measurement period and the end of the measurement period, and the numerator is the number of days covered by the prescription fills during the denominator period.¹³ Patients were classified as adherent (“met” the measure) if their PDC was at least 80% and nonadherent (“did not meet”) if their PDC was less than 80%.

For this evaluation, patients with Medicare Advantage who were in the MAH measure in the year 2023 were identified using payer-provider lists. Medicare patients were identified through prescription claims data for the same period. Patients with 2 or more prescriptions for an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker during the measurement period were extracted and matched to EHRs using their Medicare identifier. Patients who met the exclusion criteria described earlier were excluded. The PDC for each patient was calculated according to the methodology outlined by the measure steward, Pharmacy Quality Alliance.¹³

Outcomes

The primary outcome was the proportion of patients who achieved disease state control, defined as a BP less than 140/90 mm Hg at their last primary care visit in the observation year. Secondary outcomes included the proportion of patients who achieved a BP less than 130/80 mm Hg and the identification of patient and prescription factors associated with meeting the adherence measure or achieving BP less than 140/90 mm Hg. The BP goal of less than 140/90 mm Hg was selected for the primary outcome to reflect the threshold defined by commonly used quality measures, whereas the goal of less than 130/80 mm Hg reflects the 2017 American College of Cardiology/American Heart Association (ACC/AHA) guidelines, which were the most recent guidelines at the time of this evaluation. BP control outcomes were compared between patients meeting vs not meeting the adherence measure.

Data Collected

The following data elements were extracted from payer-provided reports for Medicare Advantage patients: patient birth date, medication name, adherence measure status (met vs not met), days’ supply ordered, PDC value (0-1.0), and pharmacy type used for most recent medication fill (mail-order vs brick-and-mortar). For the Medicare population, medication name, days’ supply dispensed, and fill dates were collected and used to calculate PDC. For both populations, other data were extracted from the health system’s EHR, including demographic characteristics (age, sex, patient-reported racial and ethnic group), zip code, hypertension registry status (yes/no), diabetes registry status (yes/no), depression registry status (yes/no), and most recent primary care BP measurement in calendar year 2023 and date collected. An extended medication supply was defined as any amount for more than 30 days. The zip code was used to obtain a Social Deprivation Index (SDI) score (1-100), a composite measure of area-level deprivation based on 7 domains from the American Community Survey, used to quantify socioeconomic variation in health outcomes. A higher SDI score indicates a higher level of social deprivation.¹⁴

Medical Record Review Methods

To identify possible circumstances associated with not meeting the adherence measure other than actual medication nonadherence, a manual EHR review of a randomly selected sample of nonadherent patients with uncontrolled and controlled BP was conducted to look for objectively identifiable circumstances: medication change, dose change, or medication discontinuation during the observation period.

Statistical Analysis

To summarize continuous variables, descriptive statistics including means, medians, quartiles, and SDs are provided, whereas categorical variables are presented as percentages to illustrate the distribution across different groups. Distributions of continuous variables were tested for normality, and comparisons between groups were assessed using the Wilcoxon rank sum test or t test as appropriate, whereas differences in proportions for categorical variables were evaluated using the χ² test. The outcome of hypertension control defined as a primary care BP less than 140/90 mm Hg or as less than 130/80 mm Hg was compared between patients classified as adherent or nonadherent, adjusting for potential confounders (age ≥ 75 years, sex, White race and non-Hispanic ethnicity, SDI score, use of a mail-order pharmacy, and an extended days’ supply of medication) using multivariable logistic regression. Potential confounders were selected based on prior literature indicating associations with both medication adherence and BP control, including age, sex, race, socioeconomic status, and pharmacy utilization characteristics.^11,15-18 To quantify the relationship between the outcomes of hypertension control and meeting the MAH measure with patient and prescription characteristics, 2 multivariable logistic regression analyses were performed. The outcomes of hypertension control and medication adherence (met) were each set as the dependent variable, respectively, and the potential confounders listed above were set as independent variables. Statistical analyses were performed using SAS 9.4 (SAS Institute Inc).

RESULTS

A total of 3059 Medicare Advantage patients were included in the MAH measure in 2023, and an additional 2666 Medicare patients were identified as meeting eligibility criteria, for a total of 5725 patients eligible for the measure. A total of 124 patients were excluded for not being recognized as a verified patient in our EHR system and 395 for having no primary care BP measurement in the calendar year, leaving 5206 patients included in the analysis. Of these, 4056 (77.9%) were classified as adherent. The mean age was 73.5 years, most patients (78.8%) were White, and 55.1% were women. Demographic characteristics were similar between adherent and nonadherent patients except that the adherent group had a higher proportion of individuals included in the EHR-based hypertension registry (94.7% vs 92.2%; P = .001) and fewer patients included in the depression registry (30.3% vs 33.7%; P = .03) (Table 1). Demographic characteristics differed between Medicare and Medicare Advantage patients, with a lower proportion of women (53.5% vs 56.8%; P = .01) and a higher proportion of non-Hispanic White race (87.0% vs 71.5%; P < .001) in the Medicare group. The Medicare group also had a higher proportion of individuals included in the diabetes registry (56.6% vs 33.6%; P < .001) and a lower proportion in the depression registry (30.0% vs 32.3%; P = .03). BP control was similar between the Medicare Advantage and Medicare groups, but the Medicare Advantage group had higher adherence (eAppendix [available at ajmc.com]).

Primary Outcome

Of patients who met the MAH measure, 3132 of 4056 (77.2%) achieved a BP of less than 140/90 mm Hg at their most recent primary care visit compared with 845 of 1150 (73.5%) patients who did not meet the MAH measure (OR, 1.22; 95% CI, 1.05-1.42; P = .01) (Figure). Thus, the relative likelihood of having controlled BP for patients meeting the MAH measure compared with those who did not meet it was 1.05 (P = .01).

Secondary Outcomes

Using the stricter definition of hypertension control of less than 130/80 mm Hg, 1860 of 4056 (45.9%) patients who met the MAH measure achieved control compared with 499 of 1150 (43.4%) patients who did not meet the MAH measure (OR, 1.09; 95% CI, 0.95-1.24; P = .14) (Figure). Factors associated with adherence success differed from those associated with BP control. Use of a mail-order pharmacy was associated with meeting the MAH measure (OR, 2.10; 95% CI, 1.76-2.49) and achieving a BP less than 140/90 mm Hg (OR, 1.24; 95% CI, 1.07-1.45), whereas an extended days’ supply was significantly associated with meeting MAH (OR, 1.54; 95% CI, 1.04-2.27) but not with achieving BP control (OR, 0.90; 95% CI, 0.58-1.38). Age 75 years or older was negatively associated with achieving BP control (OR, 0.86; 95% CI, 0.75-0.98) but not associated with meeting MAH (OR, 1.02; 95% CI, 0.89-1.16), and non-Hispanic White race was negatively associated with meeting the adherence measure (OR, 0.81; 95% CI, 0.69-0.96) and positively associated with achieving BP control (OR, 1.44; 95% CI, 1.24-1.68). Patient sex and SDI score were not associated with either BP control or adherence success (Table 2).

Manual EHR review was performed for 20 randomly selected nonadherent patients with PDCs ranging from 0.1 to 0.7. Ten (50%) had a RAAS antagonist dose change or had the medication discontinued for a period during the 2023 measurement year, which may have impacted their MAH performance.

DISCUSSION

In this evaluation, we found that a large proportion of patients (73.5%) who failed to meet the MAH measure achieved a primary care BP of less than 140/90 mm Hg. Although a statistically significant difference in achievement of this BP benchmark existed between the adherent vs nonadherent groups (77.2% vs 73.5%; P = .01), the relatively small absolute difference between the 2 groups suggests that this measure may not accurately correlate with meaningful patient outcomes or serve as a meaningful surrogate marker to differentiate high-value care from lower-value care. When defining BP control according to the 2017 ACC/AHA guidelines (< 130/80 mm Hg), there was no statistically significant difference in control achievement rates between those who met vs those who did not meet the MAH measure. Data from other studies have shown conflicting results of the association between MAH and BP control. A retrospective cohort observational study of patients obtained from Taiwan’s national health insurance database found a stronger relationship between adherence and BP control, with 60.0% of adherent patients having BP less than 140/90 mm Hg vs 55.8% of nonadherent patients (OR, 1.20; 95% CI, 1.13-1.29), in a younger population from an earlier time period.¹⁹ A 2018 randomized controlled trial of 411 adults showed that although a smartphone adherence app improved self-reported adherence, it did not significantly affect systolic BP.²⁰

We observed that adherence success and BP control were associated with different factors, suggesting that distinct drivers underlie each outcome. For example, non-Hispanic White race was associated with BP control, which has been reported previously.¹⁶ In contrast, non-Hispanic White race was negatively associated with meeting the MAH measure, which conflicts with the finding of a 2022 study that American Indian/Alaska Native, Hispanic, and non-Hispanic Black beneficiaries were less likely to be adherent than non-Hispanic White beneficiaries.¹⁸ Extended days’ supply has been previously found to improve adherence but was not associated with a statistical difference in BP control, which is similar to our findings.¹¹ Mail-order pharmacy use was the only factor associated with both adherence and hypertension control. Previous findings have also suggested that mail-order pharmacy use is linked to better adherence,^15,18 although no data to our knowledge are available for its association with hypertension control. Data for other chronic disease states, such as diabetes and hyperlipidemia, have indicated that mail-order pharmacy use is associated with improved disease state control.^21,22 SDI score did not play a role in either BP control or adherence success, which aligns with findings of a previous study in more than 66,000 patients at community health centers showing that reductions in BP over 5 years were not associated with SDI score.¹⁷ Other measures of social deprivation, such as eligibility for low-income subsidy, have been linked to lower adherence.^18,23

The manual chart review revealed that half the nonadherent patients had medication changes or discontinuations that could have lowered their PDC. This supports the notion that adherence measure performance can be confounded by clinically appropriate medication adjustments rather than true medication nonadherence.

Implications and Limitations

These findings have important implications for how the quality of hypertension management is assessed. A large proportion of patients may be classified as nonadherent despite being clinically well managed, which can significantly affect provider quality ratings and reimbursement in value-based arrangements. Although medication adherence measures are undoubtedly important, shifting the current heavy focus from adherence to direct measures of disease-state control could provide a more accurate reflection of high-quality care. Medication adherence measures have a well-established role in quality improvement. PDC-based measures, including MAH, were formally adopted in 2012 as part of the Medicare Part D Star Ratings program. As Shirley et al described, these measures have been instrumental in raising awareness of medication adherence as a clinical priority and have led to better access to medications through increased use of extended days’ supply and mail-order pharmacies for chronic conditions such as hypertension.²⁴ From 2012 to 2022, Medicare Advantage plans have improved their adherence measure scores by 15 percentage points for hypertension,²⁴ again underscoring the value of these measures. The high weighting of medication adherence measures has likely played a role in raising clinician and patient awareness of the importance of adherence and in improving access to chronic medications through extended days’ supplies and mail-order delivery. However, the possibility that these measures may be approaching a “topping out” point must be considered, especially in the current setting of their heavy weighting in value-based care that may drive behavior that improves the measure without improving patient care. In practice, setting a patient’s medication refills to occur automatically would result in a perfect PDC score, but it does not guarantee that the patient will ingest the medication as prescribed. Overall global adherence rates are now considered high (eg, ~87% for hypertension), and variation among providers has narrowed to the extent that meaningful differentiation is becoming more limited. Long-term sustainability and the ability to drive further improvement on medication adherence measures may be restricted without evolution.²⁴

Therefore, although adherence measurement has played a crucial role in quality improvement, the measures may need a strategic shift toward an emphasis on more outcome-driven or patient-centered approaches. For hypertension, this could include the Controlling High Blood Pressure measure or potential future utilization of self-measured BP (SMBP) data. The 2017 ACC/AHA guidelines explicitly recommend out-of-office BP measurement to confirm a diagnosis of hypertension and medication titration. SMBP allows for more real-world data on BP trends than a single in-office measurement. Although data on SMBP and quality measurement are still developing, their incorporation could address key limitations of claims-based data by providing direct insight into day-to-day hypertension status.

This evaluation has several limitations. Due to its retrospective observational design, available data were incomplete, necessitating exclusion of 395 of 5725 patients (6.9% of the population) due to missing primary care BP measurements. In addition, these results, collected within a single health system, may not be generalizable to other settings. BP control was assessed using a single primary care BP measurement, which may not reflect overall clinical control over the entire year. It is possible that some patients adhered to their medication more closely leading up to their appointment than at other times, making their BP appear well controlled but not reflecting the time when they were not taking their medication. However, the manual EHR review indicated that at least some patients classified as nonadherent may have reached that status through medication dose changes or discontinuations.

CONCLUSIONS

The likelihood of achieving BP control was minimally higher in patients classified as adherent to hypertension medications compared with patients classified as nonadherent. Different factors were associated with medication adherence than those linked to disease state control, indicating that efforts to impact MAH may not necessarily improve hypertension control. A larger emphasis on direct measures of disease state control vs the surrogate outcome of medication adherence may drive limited resources toward more clinically relevant outcomes. 

Author Affiliations: University of Colorado Anschutz Skaggs School of Pharmacy and Pharmaceutical Sciences (KTH, JJS, OT, NL, SJB), Denver, CO; University of Colorado School of Medicine (LMS, AM), Denver, CO; Trinsic Clinically Integrated Network (KNH), Broomfield, CO.

Source of Funding: This quality improvement evaluation was funded by a Pharmacy Resident Research Grant from the American Society of Health-System Pharmacists Foundation (Bethesda, MD).

Author Disclosures: Dr Schilling is on the board of the CU Medicine faculty practice plan, which participates in value-based contracts that include medication adherence performance measures. The remaining authors report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.

Authorship Information: Concept and design (KTH, JJS, NL, LMS, KNH, SJB); acquisition of data (KTH, AM, SJB); analysis and interpretation of data (KTH, JJS, OT, LMS, KNH, SJB); drafting of the manuscript (KTH, JJS, OT, SJB); critical revision of the manuscript for important intellectual content (KTH, JJS, OT, NL, LMS, KNH, SJB); statistical analysis (KTH, JJS, OT, SJB); provision of patients or study materials (AM); obtaining funding (KTH, LMS, SJB); administrative, technical, or logistic support (JJS, NL, AM); and supervision (SJB).

Address Correspondence to: Sarah J. Billups, PharmD, BCPS, University of Colorado, 12850 E Montview Blvd, Aurora, CO 80045. Email: sarah.billups@cuanschutz.edu.

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