Background: Patient long-term adherence to β-blockers, HMG-CoA reductase inhibitors (statins), and angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) after acute myocardial infarction (AMI) is alarmingly low. It is unclear how prevalent patient adherence may be across small geographic areas and whether this geographic prevalence may vary.
Methods: This is a retrospective cohort study using Medicare service claims files from 2007 to 2009 with Medicare beneficiaries 65 years and above who were alive 30 days after the index AMI hospitalization between January 1, 2008 and December 31, 2008 (N=85,017). The adjusted proportions of patients adherent to β-blockers, statins, and ACEIs/ARBs, respectively, in the 12 months after discharge across the 306 Hospital Referral Regions (HRRs) were measured and compared by control chart. The intracluster correlation coefficient (ICC) and the additional prediction power from this small-area variation on individual patient adherence were assessed.
Results: The adjusted proportion of patients adherent across HRRs ranged from 58% to 74% (median, 66%) for β-blockers, from 57% to 67% (median, 63%) for ACEIs/ARBs, and from 58% to 73% (median, 66%) for statins. The ICC was 0.053 (95% CI, 0.043-0.064) for β-blockers, 0.050 (95% CI, 0.039-0.061) for ACEIs/ARBs, and 0.041 (95% CI, 0.031-0.052) for statins. The adjusted proportion of patients adherent across HRRs increased the c-statistic by 0.01-0.02 (P < 0.0001).
Conclusions: Nonadherence to evidence-based preventive therapies post-AMI among older adults was prevalent across small geographic regions. Moderate small-area variation in patient adherence exists.