Mortality in people with mental disorders in Poland: A nationwide, register-based cohort study

BACKGROUND: Mortality among people with mental disorders is higher in comparison with the general population. There is a scarcity of studies on mortality in the abovementioned group of people in Central and Eastern European countries. METHODS: The study aimed to assess all-cause mortality in people with mental disorders in Poland. We conducted a nationwide, register-based cohort study utilizing data from two nationwide registries in Poland: the registry of healthcare services reported to the National Health Fund (2009–2018) and the all-cause death registry from Statistics Poland (2019). We identified individuals who were consulted or hospitalized in public mental healthcare facilities and received at least one diagnosis of mental disorders (International Statistical Classification of Diseases and Health Problems [ICD-10]) from 2009 to 2018. Standardized mortality ratios (SMRs) were compared between people with a history of mental disorder and the general population. RESULTS: The study comprised 4,038,517 people. The SMR for individuals with any mental disorder compared with the general population was 1.54. SMRs varied across diagnostic groups, with the highest values for substance use disorders (3.04; 95% CI 3.00–3.09), schizophrenia, schizotypal and delusional disorders (2.12; 95% CI 2.06–2.18), and pervasive and specific developmental disorders (1.68; 95% CI 1.08–2.29). When only inpatients were considered, all-cause mortality risk was almost threefold higher than in the general population (SMR 2.90; 95% CI 2.86–2.94). CONCLUSIONS: In Poland, mortality in people with mental disorders is significantly higher than in the general population. The results provide a reference point for future longitudinal studies on mortality in Poland.