Higher mortality after myocardial infarction in patients with severe mental illness: a nationwide cohort study

ObjectivesThe aim of this study was to explore the impact of severe mental illness (SMI) on myocardial infarction survival and determine the influence of risk factor burden, myocardial infarction severity and different treatments. Design, setting and participantsThis population-based cohort study, conducted in Sweden during the period 1997-2010, included all patients with a first diagnosis of myocardial infarction in the Swedish nationwide myocardial infarction register SWEDEHEART (n=209592). Exposure was defined as a diagnosis of SMI (i.e. bipolar disorder or schizophrenia) in the national patient register prior to infarction. Bias-minimized logistic regression models were identified using directed acyclic graphs and included covariates age, gender, smoking, diabetes, previous cardiovascular disease, myocardial infarction characteristics and treatment. Main outcome measuresThe outcomes were 30-day and 1-year mortality, obtained through linkage with national population registers. ResultsPatients with bipolar disorder (n=442) and schizophrenia (n=541) were younger (mean age 68 and 63years, respectively) than those without SMI (n=208609; mean age 71years). The overall 30-day and 1-year mortality rates were 10% and 18%, respectively. Compared with patients without SMI, patients with SMI had higher 30-day [odds ratio (OR) 1.99, 95% confidence interval (CI) 1.55-2.56] and 1-year mortality (OR 2.11, 95% CI 1.74-2.56) in the fully adjusted model. The highest mortality was observed amongst patients with schizophrenia (30-day mortality: OR 2.58, 95% CI 1.88-3.54; 1-year mortality: OR 2.55, 95% CI 1.98-3.29). ConclusionSMI is associated with a markedly higher mortality after myocardial infarction, also after accounting for contributing factors. It is imperative to identify the reasons for this higher mortality.