Objective — The cause of increased post-AMI (acute myocardial infarction) mortality associated with depression remains poorly elucidated. The objective of this study was to examine the extent to which self-reported cardiac functional status accounted for depression-mortality associations following AMI.
Methods — Using a prospective cohort design (n = 1941), the authors obtained self-reported measures of depression and developed profiles of the patients' pre-hospitalization cardiac risks, co-morbid conditions and drugs and revascularization procedures during or following index AMI hospitalization. To create these profiles, the patients' self-reports were retrospectively linked to no less than 12 years' worth of previous hospitalization data. Mortality rates 2 years after acute MI were examined with and without sequential risk adjustment for age, sex, income, cardiovascular risk, co-morbid conditions, selected process-of-care factors and self-reported cardiac functional status.
Results — Depression was strongly correlated with 2-year mortality rate [crude hazard ratio (HR) of severe vs. minimal depression category, 2.48 (95% CI 1.20-5.15); P = 0.01]. However, after sequential adjustment for age, sex, income and self-reported cardiac functional status, the effect of depression was greatly attenuated [adjusted HR for severe vs. minimal depression category, 1.35 (95% CI 0.63-2.87); P = 0.44]. Cardiac risk factors and non-cardiac co-morbidities had negligible explanatory effect.
Discussion — The main factor determining the increased mortality rate in depressed patients is self-reported cardiac functional status. Efforts to address increased mortality in depressed patients with cardiovascular illnesses should focus on processes that impact cardiac functional status.