Adherence to High-Intensity Statins Following a Myocardial Infarction Hospitalization Among Medicare Beneficiaries

Question  Do patients take high-intensity statins with high adherence after a myocardial infarction?

Findings  In this cohort study, 41.6% and 39.1% of patients aged 66 to 75 years and older than 75 years, respectively, who filled a high-intensity statin prescription within 30 days after a myocardial infarction hospitalization continued taking this medication with high adherence at 2 years postdischarge.

Meaning  A substantial proportion of patients filling high-intensity statin prescriptions following a myocardial infarction do not continue taking this medication with high adherence and may benefit from interventions aimed to improve high-intensity statin use.

Importance  High-intensity statins are recommended following myocardial infarction. However, patients may not continue taking this medication with high adherence.

Objective  To estimate the proportion of patients filling high-intensity statin prescriptions following myocardial infarction who continue taking this medication with high adherence and to analyze factors associated with continuing a high-intensity statin with high adherence after myocardial infarction.

Design, Setting, and Participants  Retrospective cohort study of Medicare patients following hospitalization for myocardial infarction. Medicare beneficiaries aged 66 to 75 years (n = 29 932) and older than 75 years (n = 27 956) hospitalized for myocardial infarction between 2007 and 2012 who filled a high-intensity statin prescription (atorvastatin, 40-80 mg, and rosuvastatin, 20-40 mg) within 30 days of discharge. Beneficiaries had Medicare fee-for-service coverage including pharmacy benefits.

Exposures  Sociodemographic, dual Medicare/Medicaid coverage, comorbidities, not filling high-intensity statin prescriptions before their myocardial infarction (ie, new users), and cardiac rehabilitation and outpatient cardiologist visits after discharge.

Main Outcomes and Measures  High adherence to high-intensity statins at 6 months and 2 years after discharge was defined by a proportion of days covered of at least 80%, down-titration was defined by switching to a low/moderate-intensity statin with a proportion of days covered of at least 80%, and low adherence was defined by a proportion of days covered less than 80% for any statin intensity without discontinuation. Discontinuation was defined by not having a statin available to take in the last 60 days of each follow-up period.

Results  Approximately half of the beneficiaries were women and fourth-fifths were white. At 6 months and 2 years after discharge among beneficiaries 66 to 75 years of age, 17 633 (58.9%) and 10 308 (41.6%) were taking high-intensity statins with high adherence, 2605 (8.7%) and 3315 (13.4%) down-titrated, 5182 (17.3%) and 4727 (19.1%) had low adherence, and 3705 (12.4%) and 4648 (18.8%) discontinued their statin, respectively. The proportion taking high-intensity statins with high adherence increased between 2007 and 2012. African American patients, Hispanic patients, and new high-intensity statin users were less likely to take high-intensity statins with high adherence, and those with dual Medicare/Medicaid coverage and more cardiologist visits after discharge and who participated in cardiac rehabilitation were more likely to take high-intensity statins with high adherence. Results were similar among beneficiaries older than 75 years of age.

Conclusions and Relevance  Many patients filling high-intensity statins following a myocardial infarction do not continue taking this medication with high adherence for 2 years postdischarge. Interventions are needed to increase high-intensity statin use and adherence after myocardial infarction.

The 2013 American College of Cardiology/American Heart Association cholesterol treatment guideline recommends patients aged 75 years or younger with coronary heart disease take high-intensity statins (ie, dosages associated with a low-density lipoprotein cholesterol level reduction of at least 50% in clinical trials).¹ Among patients older than 75 years of age with coronary heart disease, the guideline recommends moderate-intensity statins (ie, dosages associated with a 30% to 50% low-density lipoprotein cholesterol level reduction), with high-intensity statins considered reasonable for some older patients.¹

Adverse effects are more common among people taking high- vs low/moderate-intensity statins.² The aims of this analysis were to estimate the proportion of patients filling high-intensity statin prescriptions following a myocardial infarction (MI) hospitalization who continue taking this medication with high adherence after discharge and investigate factors associated with continuation of high-intensity statins with high adherence.

We analyzed data for 57 898 Medicare beneficiaries aged 66 years or older with an MI hospitalization (defined by an inpatient claim with a code of 410.x0/410.x1 in any diagnosis position) between January 1, 2007, and December 31, 2012, whose initial statin fill within 30 days of hospital discharge was for a high-intensity dosage (eFigure 1 in the Supplement). We excluded younger beneficiaries because their main reasons for being Medicare eligible are disability and end-stage renal disease. We also excluded beneficiaries whose initial statin fill was simvastatin, 80 mg, because this formulation is no longer recommended.³ All beneficiaries had continuous fee-for-service coverage from 1 year before through 6 months after their MI hospitalization. Only the first MI for each beneficiary was analyzed. The institutional review board at the University of Alabama at Birmingham approved the study. A waiver of informed consent was granted for the use of deidentified data.

We used Medicare data to identify patient characteristics and health resource use prior to, during, and after the MI (eTable 1 in the Supplement). Prescription fills for low-, moderate-, and high-intensity statins were identified using Medicare pharmacy claims (eTable 2 in the Supplement). Beneficiaries with and without a high-intensity statin fill in the year prior to their MI were defined as prevalent and new users, respectively.

We analyzed patterns of statin use at 6 months, 1 year, 18 months, and 2 years after the MI, restricted to beneficiaries who had continuous fee-for-service coverage during these times (eFigure 2 in the Supplement). Patterns analyzed at 6 months after discharge included:

• Continuing to take high-intensity statins with high adherence: proportion of days covered of at least 80% for high-intensity statins without low/moderate-intensity statin prescription fills within 6 months after discharge and with a statin available to take in the last 60 days of the 6-month period. Proportion of days covered was calculated using the interval-based method, excluding days spent in the hospital.⁴

• Down-titrating to low/moderate-intensity statins with high adherence: low/moderate-intensity statin prescription fill during the 6 months after discharge without subsequent high-intensity statin prescription fills, proportion of days covered of at least 80% from the first low/moderate-intensity statin fill through 6 months after discharge, and a statin available to take in the last 60 days of the 6-month period.

• Statin use with low adherence: proportion of days covered less than 80% for high- or low/moderate-intensity statins with a statin available to take in the last 60 days of the 6-month period.

• Discontinuation of statins: not having a statin available to take in the last 60 days of the 6-month period.

• Other patterns of statin use: not meeting any of the previously mentioned definitions (eg, down-titration to low/moderate-intensity statins followed by up-titration back to a high-intensity statin).

Analogous definitions were used to analyze statin use patterns at 1 year, 18 months, and 2 years.

Beneficiaries aged 66 to 75 years and older than 75 years were analyzed separately. We calculated patterns of statin use following hospital discharge in the overall population among patients with an MI in 2007 and 2012 and among prevalent and new high-intensity statin users. Also, we calculated patterns of statin use at 1 year, 18 months, and 2 years postdischarge restricted to beneficiaries who continued taking high-intensity statins with high adherence, down-titrated to a low/moderate-intensity statin with high adherence, took statins with low adherence, and discontinued their statin at 6 months.

We calculated patient characteristics and health resource use by patterns of statin use at 6 months after discharge. We calculated multivariable-adjusted prevalence ratios for taking high-intensity statins with high adherence at 6 months associated with patient characteristics and health resource use. We also calculated prevalence ratios for taking high-intensity statins with high adherence at 2 years following hospital discharge overall and conditional on taking a high-intensity statin with high adherence at 6 months. Factors associated with taking high-intensity statins with high adherence were also analyzed among prevalent and new high-intensity statin users, separately.

Among beneficiaries 66 to 75 years of age, 17 633 (58.9%) continued taking a high-intensity statin with high adherence, 2605 (8.7%) down-titrated to a low/moderate-intensity statin with high adherence, 5182 (17.3%) had low statin adherence, and 3705 (12.4%) discontinued their statin at 6 months after discharge (Figure 1). Progressively fewer beneficiaries continued taking a high-intensity statin with high adherence at 1 year, 18 months, and 2 years. The proportion of beneficiaries taking high-intensity statins with high adherence after discharge increased between 2007 and 2012 (eFigure 3 in the Supplement). New high-intensity statin users were less likely to continue taking high-intensity statins with high adherence vs prevalent users (eFigure 4 in the Supplement). Among beneficiaries taking high-intensity statins with high adherence at 6 months postdischarge, 9547 (64.0%) continued taking a high-intensity statin with high adherence at 2 years (eFigure 5 in the Supplement). Few beneficiaries taking statins with low adherence or who discontinued statin therapy at 6 months were taking high- or low/moderate-intensity statins with high adherence at 1 year, 18 months, and 2 years. Results were similar among beneficiaries older than 75 years of age (eFigures 6-9 in the Supplement).

Characteristics of beneficiaries by their pattern of statin use at 6 months after discharge is shown in the Table for those aged 66 to 75 years and eTable 3 in the Supplement for those older than 75 years. After multivariable adjustment, the probability of continuing to take a high-intensity statin with high adherence at 6 months and 2 years after discharge increased from 2007 to 2012 and was higher among beneficiaries with dual Medicare/Medicaid coverage, cardiac rehabilitation, more cardiologist visits, and a medication coverage gap after discharge (Figure 2; eFigure 10 in the Supplement for beneficiaries 66-75 years and older than 75 years, respectively). In contrast, African American patients, Hispanic patients, and new high-intensity statin users were less likely to continue taking a high-intensity statin with high adherence. Factors associated with continuing to take a high-intensity statin with high adherence were consistent for prevalent and new high-intensity statin users (eFigures 11-14 in the Supplement).

In this study, most Medicare beneficiaries who filled a high-intensity statin prescription following an MI hospitalization did not continue taking this medication with high adherence for 2 years after discharge. Several patient and health resource use characteristics were associated with continuing high-intensity statins with high adherence. These factors could inform interventions to reduce residual cardiovascular risk after MI.

Risk for recurrent coronary heart disease events is high after an MI.⁵ However, between 2007 and 2011, less than 30% of Medicare beneficiaries 65 to 74 years of age filled a high-intensity statin prescription within 90 days after a coronary heart disease–related hospitalization.⁶ Results from this analysis show that many patients who fill a high-intensity statin prescription after an MI do not continue taking this medication with high adherence. Suboptimal adherence to high-intensity statins has been reported among patients 18 years of age or older with commercial health insurance or Medicare coverage in the Marketscan database.⁷

In a prior study, statin adherence was higher among patients with vs without a physician visit within 6 weeks following an MI hospitalization.⁸ Follow-up visits after an MI allow physicians to assess medication adherence and identify factors associated with low statin adherence including adverse effects, perceived lack of efficacy, and cost issues.^1,9 This analysis suggests that African American individuals, Hispanic individuals, and new high-intensity statin users may have a larger benefit from monitoring adherence to high-intensity statins after MI.

The association between reaching the Medicare medication coverage gap and high-intensity statin use with high adherence may be owing to high medication adherence being associated with greater costs. Dual Medicare/Medicaid coverage and postdischarge cardiologist visits and cardiac rehabilitation were associated with continuing to take a high-intensity statin with high adherence. These results are consistent with prior studies showing that a lower medication copayment, cardiology visits, and cardiac rehabilitation are associated with higher statin use.^10-13 Full coverage of medications, including statins, was effective in reducing the risk for major vascular events or revascularization after an MI in a cluster-randomized trial.¹⁴ In another trial, randomization to cardiac rehabilitation vs usual care increased adherence to lipid-lowering medication at 3 months and lowered cholesterol levels at 6 months following MI hospitalization.¹⁵

This study has potential limitations. Use of pharmacy claims may result in misclassification of statin use patterns because some beneficiaries may not take the medication they filled while others may receive free samples. Other factors not considered in this analysis, including characteristics of the hospital where the patient was treated for their MI, may be associated with patterns of statin use. Reasons for statin down-titration or discontinuation were not analyzed because these data are not available in Medicare claims.

Results from this study indicate that many patients who fill a high-intensity statin following an MI hospitalization do not continue taking this medication with high adherence during the 2 years postdischarge. Lower medication costs, cardiologist visits, and cardiac rehabilitation may contribute to improving high-intensity statin use and adherence after myocardial infarction.

Corresponding Author: Robert S. Rosenson, MD, Icahn School of Medicine at Mount Sinai, 1425 Madison Ave, MC1 Level, Hospital Box 1030, New York, NY 10029 (robert.rosenson@mssm.edu).

Accepted for Publication: February 24, 2017.

Published Online: April 19, 2017. doi:10.1001/jamacardio.2017.0911

Author Contributions: Drs Colantonio amd Huang had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Colantonio, Monda, Bittner, Taylor, Brown, Glasser, Muntner, Rosenson.

Acquisition, analysis, or interpretation of data: Colantonio, Huang, Bittner, Serban, Taylor, Brown, Glasser, Muntner, Rosenson.

Drafting of the manuscript: Colantonio, Muntner, Rosenson.

Critical revision of the manuscript for important intellectual content: Huang, Monda, Bittner, Serban, Taylor, Brown, Glasser, Muntner, Rosenson.

Statistical analysis: Colantonio, Huang, Muntner.

Obtained funding: Monda, Muntner.

Administrative, technical, or material support: Monda, Taylor, Muntner, Rosenson.

Supervision: Monda, Brown, Glasser, Muntner, Rosenson.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Monda and Taylor are employed by Amgen Inc. Drs Bittner, Brown, Glasser, Muntner, and Rosenson receive research support from Amgen Inc. Dr Bittner also receives research support from Astra-Zeneca, DalCor, Sanofi-Regeneron, Pfizer, and Bayer Healthcare, and has served on advisory panels for Amgen and Eli Lilly. Dr Brown also receives research support from Astra-Zeneca. Dr Rosenson also receives research support from Amgen, Astra Zeneca, Eli Lilly, Esperion, Medicines Company, Regeneron, and Sanofi and serves on Advisory Boards for Akcea, Amgen Inc, Astra Zeneca, Eli Lilly, Regeneron, and Sanofi. No other disclosures are reported.

Funding/Support: The design and conduct of the study, analysis, and interpretation of the data, and preparation of the manuscript, was supported through a research grant from Amgen Inc (Thousand Oaks, California).

Role of the Funder/Sponsor: The funding source had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.