Are AMI patients with comorbid mental illness more likely to be admitted to hospitals with lower quality of AMI care?

Objective: Older patients with comorbid mental illness are shown to receive less appropriate care for their medical conditions. This study analyzed a national cohort of Medicare patients hospitalized for acute myocardial infarction (AMI), and determined whether those with comorbid mental illness were more likely to present to hospitals with lower quality of AMI care. We further compared differences in outcomes (length of stay, short-term readmissions, and short-term and long-term mortality) between mentally-ill and mentally-intact patients admitted to hospitals of different quality groups.

Methods: Retrospective analyses of Medicare claims in 2008. Hospital quality was measured using the five “Hospital Compare” process indicators (aspirin at admission and discharge, beta-blocker at admission and discharge, and angiotension-converting enzyme inhibitor or angiotension receptor blocker for left ventricular dysfunction). Multinomial logit models controlled for patient and hospital covariates, and determined the independent association of mental illness with admission to low-quality hospitals (rank of the composite process score <10th percentile) or high-quality hospitals (rank>90th percentile), compared to admissions to other hospitals with medium quality. Multivariate analyses further determined the effects of hospital type and mental diagnosis on outcomes.

Results: Among all AMI admissions to 2,845 hospitals, 41,044 patients were diagnosed with mental illness, and 246,837 patients were not. Mental illness predicted a higher likelihood of admission to low-quality hospitals (unadjusted rate 2.9% vs. 2.0%; adjusted odds ratio [OR]1.25, 95% confidence interval [CI] 1.17-1.34, p<0.01), and an equal likelihood to high-quality hospitals (unadjusted rate 9.8% vs. 10.3%; adjusted OR 0.97, 95% CI 0.93-1.01, p=0.11). Both lower hospital quality and mental diagnosis predicted higher rates of 30-day readmission, 30-day mortality, and 1-year mortality.

Conclusions: Among Medicare myocardial infarction patients, comorbid mental illness was associated with an increased risk for admission to lower-quality hospitals. Both lower hospital quality and mental illness predicted worse post-AMI outcomes. These findings suggest that the disparities in AMI care and outcomes among the mentally ill are in part a system problem. Targeted interventions at particular hospitals (e.g., improve the overall quality of low-performing hospitals) and mentally-ill patients (e.g., improve access to high-quality hospitals) would both address the disparities.