Relationship Between Medication Adherence and Other Medicare Star Rating Measures

ABSTRACT

Objectives: To assess the interrelation between Medicare Star Ratings medication adherence measures and other intermediate and process measures.

Study Design: A cross-sectional analysis was performed of the annual Medicare Star Ratings health plan performance data from Star Ratings years 2015-2025. The analysis evaluated the potential relationship between (1) renin-angiotensin system antagonist (RASA) adherence and controlling blood pressure, (2) noninsulin antidiabetic adherence and controlling blood glucose, (3) statin adherence and statin therapy for patients with cardiovascular disease (CVD), and (4) statin adherence and statin use in persons with diabetes (SUPD).

Methods: The outcomes of interest were ORs and 95% CIs evaluating the likelihood of a health plan achieving 5 stars or at least 4 stars on the intermediate or process measures if they achieved 5 stars or at least 4 stars on the medication adherence measures compared with not achieving 5 stars or at least 4 stars on the medication adherence measures.

Results: Plans that achieved 5 stars on the antidiabetic adherence measure and RASA adherence measure had significantly higher odds of achieving 5 stars on their respective intermediate measures (blood glucose control: OR, 3.50; 95% CI, 2.98-4.12; blood pressure control: OR, 4.61; 95% CI, 3.82-5.60). Plans that achieved 5 stars on the statin adherence measure had significantly higher odds of achieving 5 stars on statin therapy for patients with CVD and SUPD (CVD: OR, 4.68; 95% CI, 3.49-6.27; SUPD: OR, 4.37; 95% CI, 3.26-5.85).

Conclusions: Medicare Star Ratings medication adherence measures are significantly tied to intermediate and statin process measures. Targeted interventions to improve adherence should be a key strategy for health plans to enhance both clinical outcomes and financial incentives.

Am J Manag Care. 2025;31(11):In Press

Takeaway Points

Medicare health plans improving performance on the Medicare Star Ratings medication adherence measures have the potential to concurrently improve performance on the Part C intermediate outcome measures and statin process measures.

• Plans achieving 5 stars on the diabetes adherence measure were 3.5 times more likely to achieve 5 stars on the controlling blood glucose measure.
• Plans achieving 5 stars on the measure of renin-angiotensin system antagonist adherence were 4.6 times more likely to achieve 5 stars on the controlling blood pressure measure.
• Plans achieving 5 stars on the statin adherence measure were 4.7 times more likely to achieve 5 stars on the measure of statin therapy for patients with cardiovascular disease and 4.4 times more likely to achieve 5 stars on the measure of statin use in persons with diabetes.

To evaluate Medicare health plan performance, CMS introduced the Medicare Star Ratings program in 2007.1 This program evaluates the quality and performance of Medicare Part C (Medicare Advantage) and Part D (prescription drug) plans. Each plan is assessed using a set of quality measures, which are individually assigned a weight from 1 to 5 and a performance rating from 1 to 5 stars. A rating of 5 stars signifies the highest performance.2 Plans then receive summary ratings for the Part C measures and Part D measures and an overall summary rating for all measures.2 These quality measures, along with their respective weights and cut-point thresholds for achieving specific stars for each measure, are updated annually, allowing for variability from year to year in the Medicare Star Ratings.2

The upcoming 2026 Medicare Star Ratings will include 45 total quality measures (33 Part C measures and 12 Part D measures).3 To incentivize health plans to focus on Star Ratings, CMS ties Medicare health plan reimbursement to their performance on these ratings. Higher-performing plans receive greater reimbursement rates, and plans achieving at least a 4-star overall summary rating are eligible for a 5% quality bonus payment (QBP).4

Three specific Part D measures focus on medication adherence, specifically assessing adherence to noninsulin antidiabetics, renin-angiotensin system antagonists (RASAs), and statins, with each measure weighted at 3.2 Adherence to these classes of medications has been shown to reduce health care resource utilization (HCRU) and health care costs in the Medicare population, with these analyses using a 1-year time horizon demonstrating that beneficiaries who were adherent had lower HCRU and costs than those who were nonadherent during the year assessed.5-7 Research further suggests that improving adherence to the medications targeted by Star Ratings also increases adherence to other nontargeted chronic medications.8 Because medication adherence plays a significant role in reducing health care costs, payers and pharmacy benefit managers often focus their attention on improving these measures for their health plan because several interventions have been demonstrated to successfully improve adherence and enhance Star Ratings performance.9-13

When reviewing the list of remaining quality measures, several appear to have a potential interrelation with the adherence measures. These include a Part C intermediate measure of controlling blood pressure with the Part D RASA adherence measure, a Part C intermediate measure of controlling blood glucose with the Part D noninsulin antidiabetic adherence measure, a Part C process measure of statin utilization in patients with cardiovascular disease (CVD), and a Part D process measure of statin use in persons with diabetes (SUPD), with the latter 2 measures appearing to have a potential relation with the statin adherence measure.2 Given the importance of performance on the Medicare Star Ratings for Medicare health plans and the potential to help promote medication adherence through different initiatives, it is necessary to assess whether health plans may see benefits on additional Star Ratings measures from high performance on the adherence measures.

METHODS

A cross-sectional analysis was performed of the publicly available annual Medicare Star Ratings health plan performance data from CMS for the Star Ratings years 2015-2025.14 Plans were excluded each year if their rating on the measures of interest were “not applicable,” “no data available,” “not enough data available,” or “plan not required to report measure.” The analysis sought to evaluate the potential relationship between (1) performance on the RASA adherence measure and performance on the intermediate measure of controlling blood pressure, (2) performance on the measure for noninsulin antidiabetic adherence and performance on the intermediate measure of controlling blood glucose, (3) performance on the statin adherence measure and performance on the process measure of statin therapy for patients with CVD, and (4) performance on the statin adherence measure and performance on the process measure of SUPD (eAppendix Figure [available at ajmc.com]).

The analysis of the RASA adherence measure used data from the Star Ratings years 2015-2025, except for 2020 to 2022 because the Part C blood pressure measure was not included in those Medicare Star Ratings. The noninsulin antidiabetic analysis used the Star Ratings years 2015-2025. Both statin analyses used data from the Star Ratings years 2019-2025 because these 2 statin process measures were first included in the 2019 Star Ratings.14

The primary outcomes of interest were the ORs and 95% CIs evaluating the likelihood of a health plan achieving 5 stars or at least 4 stars on the intermediate or process measures if they achieved 5 stars or at least 4 stars on the medication adherence measures compared with not achieving 5 stars or at least 4 stars on the medication adherence measures. The ORs and 95% CIs were calculated using OpenEpi 3.01 (Open Source Epidemiologic Statistics for Public Health).

RESULTS

The 11-year assessment of the diabetes measures included 4544 health plan contracts (Table). Plans that achieved 5 stars or at least 4 stars on the adherence measure had significantly higher odds of achieving 5 stars or at least 4 stars on the intermediate measure (5 stars: OR, 3.50; 95% CI, 2.98-4.12; ≥ 4 stars: OR, 2.21; 95% CI, 1.93-2.53) (Figure).

During the 8-year assessment of the blood pressure measures, 3279 health plans were included. Plans that achieved 5 stars or at least 4 stars on the RASA adherence measure had significantly higher odds of achieving 5 stars or at least 4 stars on the blood pressure intermediate measure (5 stars: OR, 4.61; 95% CI, 3.82-5.60; ≥ 4 stars: OR, 4.43; 95% CI, 3.83-5.13).

During the 7-year analysis of the statin measures, 2852 health plan contracts were included. Health plans that achieved 5 stars or at least 4 stars on the statin adherence measure had significantly higher odds of achieving 5 stars or at least 4 stars on the statin therapy for patients with CVD measure (5 stars: OR, 4.68; 95% CI, 3.49-6.27; ≥ 4 stars: OR, 2.70; 95% CI, 2.32-3.15). Health plans that achieved 5 stars or at least 4 stars on the statin adherence measure also had significantly higher odds of achieving 5 stars or at least 4 stars on the SUPD measure (5 stars: OR, 4.37; 95% CI, 3.26-5.85; ≥ 4 stars: OR, 1.36; 95% CI, 1.16-1.58).

DISCUSSION

The results of this analysis showed that health plans performing well on the medication adherence measures had a significantly higher likelihood of performing well on potentially related Part C intermediate outcome measures and statin process measures. This reinforces the notion that improving medication adherence measures may contribute to better performance on additional measures, thus helping to improve health outcomes. Moreover, the connection between different measures indicates that enhancing performance on adherence measures can lead to high performance on additional measures, ultimately increasing the likelihood of both overall performance and revenue. The correlation between medication adherence and overall plan performance suggests that targeted interventions to improve adherence could substantially improve both financial and clinical outcomes for health plans. This has potential implications for health policy and reimbursement structures in value-based care models.

These findings offer benefits for various payer stakeholders. Performance on the Medicare Star Ratings is directly tied to financial reimbursements and payments from CMS. Plans with an overall summary rating of 4.5 or 5 stars receive a 70% rebate, whereas those with overall summary ratings of 3.5 or 4 stars receive a 65% rebate and those with overall summary rating of 3 or fewer stars receive a rebate of only 50%.4 Additionally, plans that receive at least 4-star overall summary ratings qualify for a QBP of 5%, which equated to $30 per member per month in 2024.15 Furthermore, research has shown that increases in Medicare Star Ratings lead to increases in health plan enrollment, resulting in increased revenue for the health plan.16 Based on these factors, Medicare health plans have a financial incentive to perform as well as possible on the Medicare Star Ratings.

Our findings demonstrating positive correlations between the Part D adherence measures and Part C intermediate measures are consistent with previous research. A cross-sectional logistic regression analysis of the 2015 Medicare Star Ratings found that each percentage-point increase in medication adherence was associated with a significantly increased likelihood of health plans ranking in the top quartile of plan performance for the corresponding Part C intermediate measure.17 Specifically, the analysis revealed an adjusted OR (AOR) of 4.63 (95% CI, 2.72-7.89) for the RASA adherence measure and Part C controlling blood pressure measure and an AOR of 4.69 (95% CI, 2.79-7.91) for the diabetes adherence measure and Part C controlling glucose measure.17 Our study, which analyzed a more extended time period (8 years for the blood pressure measures and 11 years for the diabetes measures), corroborates these findings across a larger sample. We found that achieving 5 stars on the RASA adherence measure had an OR of 4.61 (95% CI, 3.82-5.60) for achieving 5 stars on the corresponding Part C intermediate measure. Similarly, achieving 5 stars on the diabetes adherence measure had an OR of 3.50 (95% CI, 2.98-4.12) for achieving 5 stars on the corresponding Part C intermediate measure. These results show that improving performance on medication adherence measures may drive better outcomes on related intermediate measures, which in turn improves overall health plan performance.

This analysis underscores the importance of strong performance on medication adherence measures because it can correlate with improved outcomes on other Medicare Star Ratings. This relationship suggests that plans excelling in adherence measures have an increased likelihood of high overall plan performance. For the 2026 Medicare Star Ratings, 45 quality measures are used, with a total weighted value of 81 stars.3 The 3 medication adherence measures account for a weight of 9 stars, and the 2 intermediate measures contribute a combined weight of 6 stars (3 each).3 Additionally, the 2 statin process measures account for a weight of 2 stars (1 each).3 Together, the adherence measures, statin process measures, and Part C intermediate measures account for a weight of 17 of 81 stars in the 2026 Star Ratings (21% of weighted stars).3 Therefore, plans that perform well on medication adherence measures have a significantly higher likelihood of performing well on the Part C intermediate measures and statin process measures, ultimately increasing the likelihood of high overall Star Ratings and receiving QBPs and higher rebates. However, it is important to note that the Star Ratings use different years’ data (and therefore potentially different patient populations) for different measures. Specifically, measures utilizing the Consumer Assessment of Healthcare Providers and Systems (CAHPS) data source or call center data source use data from the year prior to the specific Star Ratings year, whereas all other measures use data from 2 years prior (ie, for the 2024 Star Ratings, the measures using CAHPS utilize data from 2023 while all other measures use data from 2022). Although all the measures included in this analysis used the data from the same time frame, it is important to note this caveat when discussing the impact on overall plan performance and the potential delayed financial benefits.

Given the impact that performance on medication adherence measures has on overall plan performance, payers and health plans can implement several initiatives to promote medication adherence among their beneficiaries. These initiatives include blister packaging,9 refill reminders,10 90-day refill programs,10,18 prescriber outreach,10 and pharmacist counseling, including medication therapy management.11,19 These strategies have been shown to increase medication adherence rates, specifically improving performance in Medicare Star Ratings. Payers may benefit from implementing more than one of these adherence-promoting initiatives simultaneously, leading to increased medication adherence and improved Star Ratings performance. Future research should explore the specific interventions that can optimize adherence in different health plan populations and settings as well as their long-term impact on Star Ratings and patient outcomes.

Limitations

Several limitations exist with this analysis. First, this was a cross-sectional analysis of annual health plan performance and did not account for prior-year performance. Previous research has demonstrated that health plans with high Star Ratings performance that achieve QBPs have been able to reinvest those funds into initiatives to promote both population health and plan performance, such as reducing premiums or providing different clinical programs.16 This can potentially lead to these plans continuing to have high performance. This analysis also did not adjust for any plan demographics, which may potentially impact the likelihood of plan performance on certain quality measures. Health plan size may impact a plan’s performance on certain Star Ratings measures; however, the data set assessed did not include the number of beneficiaries per plan, so this information could not be included in the analysis. Additionally, this study could not assess the impact of the sociodemographic makeup of specific health plans on measure performance.

CONCLUSIONS

Medicare Star Ratings medication adherence measures are significantly tied to Part C intermediate and statin process measures. Targeted interventions to improve adherence should be a key strategy for health plans to enhance both clinical outcomes and financial incentives. These findings suggest that improving adherence could play a central role in shaping health policy and advancing value-based care initiatives. 

Author Affiliations: Becton, Dickinson and Company, San Diego, CA (EPB, IB), Durham, NC (PS, NEB), and Franklin Lakes, NJ (JDL).

Source of Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author Disclosures: Drs Saad, Barnes, Beer, and Lucaci are employed by Becton, Dickinson and Company, which manufactures blister-packaging and pouch-packaging automated technology. Dr Borrelli was employed by Becton, Dickinson and Company during the time of this study. Drs Beer and Lucaci are also shareholders of Becton, Dickinson and Company.

Authorship Information: Concept and design (EPB, PS, NEB, JDL); acquisition of data (EPB); analysis and interpretation of data (EPB, PS, NEB, IB); drafting of the manuscript (EPB); critical revision of the manuscript for important intellectual content (EPB, PS, NEB, IB, JDL); statistical analysis (EPB); administrative, technical, or logistic support (EPB, JDL); and supervision (EPB, IB, JDL).

Address Correspondence to: Eric P. Borrelli, PhD, PharmD, MBA, Becton, Dickinson and Company, 3750 Torrey View Ct, San Diego, CA 92130. Email: ericborrelli@gmail.com.

REFERENCES

1. Improving Medicare Advantage Quality Measurement. Better Medicare Alliance; October 2018. Accessed October 22, 2024. https://bettermedicarealliance.org/wp-content/uploads/2020/03/BMA_StarRatings_WhitePaper_2018_10_24.pdf

2. Medicare 2025 Part C & D Star Ratings Technical Notes. CMS. Updated October 3, 2024. Accessed October 21, 2024. https://www.cms.gov/files/document/2025-star-ratings-technical-notes.pdf

3. 2026 Star Ratings measures and weights. CMS. Accessed October 21, 2024. https://www.cms.gov/files/document/2026-star-ratings-measures.pdf

4. Advance Notice of Methodological Changes for Calendar Year (CY) 2024 for Medicare Advantage (MA) Capitation Rates and Part C and Part D Payment Policies. CMS; February 1, 2023. Accessed October 21, 2024. https://www.cms.gov/files/document/2024-advance-notice-pdf.pdf

5. Campbell PJ, Axon DR, Taylor AM, et al. Hypertension, cholesterol and diabetes medication adherence, health care utilization and expenditure in a Medicare supplemental sample. Medicine (Baltimore). 2021;100(35):e27143. doi:10.1097/MD.0000000000027143

6. Axon DR, Vaffis S, Chinthammit C, et al. Assessing the association between medication adherence, as defined in quality measures, and disease-state control, health care utilization, and costs in a retrospective database analysis of Medicare supplemental beneficiaries using statin medications. J Manag Care Spec Pharm. 2020;26(12):1529-1537. doi:10.18553/jmcp.2020.26.12.1529

7. Poonawalla IB, Chung L, Shetler S, Pearce H, Dixon SW, Racsa P. Medication adherence Star Ratings measures, health care resource utilization, and cost. Am J Manag Care. 2024;30(5):210-217. doi:10.37765/ajmc.2024.89538

8. Parekh N, Munshi KD, Hernandez I, Gellad WF, Henderson R, Shrank WH. Impact of Star Rating medication adherence measures on adherence for targeted and nontargeted medications. Value Health. 2019;22(11):1266-1274. doi:10.1016/j.jval.2019.06.009

9. Borrelli EP, Saad P, Barnes N, Dumitru D, Lucaci JD. Estimating the economic impact of blister-packaging on medication adherence and health care costs for a Medicare Advantage health plan. J Manag Care Spec Pharm. 2024;30(12):1442-1454. doi:10.18553/jmcp.2024.24179

10. Leslie RS, Gilmer T, Natarajan L, Hovell M. A multichannel medication adherence intervention influences patient and prescriber behavior. J Manag Care Spec Pharm. 2016;22(5):526-538. doi:10.18553/jmcp.2016.22.5.526

11. Leslie RS, Tirado B, Patel BV, Rein PJ. Evaluation of an integrated adherence program aimed to increase Medicare Part D Star Rating measures. J Manag Care Spec Pharm. 2014;20(12):1193-1203. doi:10.18553/jmcp.2014.20.12.1193

12. Spears J, Erkens J, Misquitta C, Cutler T, Stebbins M. A pharmacist-led, patient-centered program incorporating motivational interviewing for behavior change to improve adherence rates and Star Ratings in a Medicare plan. J Manag Care Spec Pharm. 2020;26(1):35-41. doi:10.18553/jmcp.2020.26.1.35

13. Worrall C, Shirley D, Bullard J, Dao A, Morrisette T. Impact of a clinical pharmacist-led, artificial intelligence-supported medication adherence program on medication adherence performance, chronic disease control measures, and cost savings. J Am Pharm Assoc (2003). 2025;65(1):102271. doi:10.1016/j.japh.2024.102271

14. Part C and D performance data. CMS. Updated September 10, 2024. Accessed October 15, 2024. https://www.cms.gov/medicare/health-drug-plans/part-c-d-performance-data

15. Fuglesten Biniek J, Freed M, Damico A, Neuman T. Medicare Advantage quality bonus payments will total at least $11.8 billion in 2024. KFF. September 11, 2024. Accessed October 16, 2024. https://web.archive.org/web/20241009031237/https://www.kff.org/medicare/issue-brief/medicare-advantage-quality-bonus-payments-will-total-at-least-11-8-billion-in-2024/

16. Borrelli EP, Park MA, Leslie RS. Impact of Star Ratings on Medicare health plan enrollment: a systematic literature review. J Am Pharm Assoc (2003). 2023;63(4):989-997.e3. doi:10.1016/j.japh.2023.03.009

17. Ta JT, Erickson SC, Qiu WA, Patel BV. Is there a relationship between Part D medication adherence and Part C intermediate outcomes Star Ratings measures? J Manag Care Spec Pharm. 2016;22(7):787-795. doi:10.18553/jmcp.2016.22.7.787

18. Ameli N, Jones WN. Evaluating medication day-supply for improving adherence and clinical biomarkers of hemoglobin A1c, blood pressure, and low-density lipoprotein. J Pharm Pract. 2024;37(1):140-145. doi:10.1177/08971900221129424

19. Hale G, Moreau C, Joseph T, et al. Improving medication adherence in an ACO primary care office with a pharmacist-led clinic: a report from the ACORN SEED. J Pharm Pract. 2021;34(6):888-893. doi:10.1177/0897190020934271