Mental disorder comorbidity and in-hospital mortality among patients with acute myocardial infarction

Objective: The purpose of this study was to examine the association between mental disorder comorbidity and in-hospital mortality, and whether subgroups of mental disorder comorbidity have differential impacts on in-hospital mortality in acute myocardial infarction (AMI) patients. Methods: A cross-sectional study was conducted using the 2010 Nationwide Inpatient Sample (NIS) database of the Healthcare Cost and Utilization Project (HCUP). The study sample included discharges for which the primary diagnosis was AMI. As the primary exposure, the presence of any mental disorder comorbidity was identified as discharges for which one or more mental disorders listed as the non-primary diagnosis. The secondary exposure was subgroups of the mental disorder comorbidity (schizophrenia, major affective disorder, substance abuse, and other). The outcome of interest was in-hospital mortality. Logistic regression and resulting odds ratios (ORs) with associated 95% confidence intervals (CIs) were used to estimate the impact of mental disorder comorbidity on in-hospital death. Results: A total of 42,416 discharges were included in the analysis. Of these, 16,140 (38%) had at least one diagnosis of a mental disorder. No significant differences were observed in in-hospital mortality between patients with and without mental disorder comorbidity. However, when the mental disorder comorbidity is specified into subgroups, the impact differentiated depending on the subgroup. More specifically, patients with schizophrenia were associated with increased in-hospital mortality (OR 1.72, 95% CI 1.02-2.90) and patients with substance abuse disorder were associated with decreased in-hospital mortality (OR 0.80, 95% CI 0.70-0.91). Major affective disorder and other mental disorders were not statistically significant. Conclusions: Mental disorder comorbidity has a differential impact on post-AMI in-hospital mortality depending on the subgroup of mental disorders. We argue that mental disorder comorbidity should not be treated as a single category when assessing its impact on a health outcome.