Causes of death associated with psychiatric illness

Abstract

Background: A prospective cohort analysis of mortality, among entrants to a population-based psychiatric case register, was undertaken to identify specific causes of death responsible for the increased risk of mortality previously reported in this large group of unselected patients.

Methods: The analysis was based on a study population of 16,871 cases, aged 15-89 years, from Worcester and Kidderminster Health Districts, entering the case register between 1974 and 1984 and generating a total of 85,073 patient-years (PYR) of observation. The underlying cause of death was coded to the relevant revision of the International Classification of Diseases (ICD). Numbers of deaths observed in the study population were compared with the number of deaths expected on the basis of mortality rates for England and Wales. Comparisons were made for eight main causes of death, aggregated at Chapter level of the ICD, and 11 categories of psychiatric diagnoses. Two indices of mortality were used for evaluation: relative risk (RR) = observed deaths/expected deaths; and excess mortality rate (EMR) = (observed-expected deaths)/PYR.

Results: RRs were significantly raised for accidents, including suicides, as anticipated, and for various main causes of death. The increased risk of accidental death was found across the majority of the 11 psychiatric diagnostic groups although the EMRs were low at less than 5/1000 PYR. Deaths from respiratory disorders gave rise to the highest RRs after accidental deaths, and were responsible for substantial excess mortality among in-patients and patients with psychotic illnesses (especially dementia). The largest numbers of deaths of both sexes were due to diseases of the circulatory system, with a 40 per cent excess of observed over expected values in the whole series. The excess was due mainly to deaths of in-patients and of patients with psychotic diagnoses. No excess of deaths owing to neoplasms was found for either in-patients or out-patient groups.

Conclusions: The findings that psychiatric illness is associated with an increased risk of death from "natural' causes and that the level of risk was related to the severity and to the diagnostic category of the illness have implications for patterns of care and use of resources.