Iowa record-linkage study: death rates in psychiatric patients

The Iowa record-linkage study was developed to investigate death rates in psychiatric patients, and involved computer matching of death certificates with a roster of patients. A list of all patients admitted to our hospital from 1972 through 1981 was obtained and after removing duplicate entries the list was pared to 5412 names. The record included multiple identifiers (e.g., name, gender, date-of-birth, hospital number). This information was then linked by computer with all Iowa death certificates for the same period; a total of 331 deaths were identified. Patients were assigned to a single psychiatric diagnostic category based on a computer program that reviewed each patient's clinical diagnoses and picked the one with the highest priority in a hierarchy we had created. Age and sex adjusted mortality tables were constructed, allowing us to compute expected numbers of deaths. Relative risk for premature death was greatest among women, and those under 20 years. Risk was associated with all psychiatric diagnoses and was significantly higher among patients of either gender with an organic mental disorder or schizophrenia; women with acute schizophrenia, depressive neuroses, alcoholism, drug abuse, and psychophysiological disorders; and men with neuroses. Death from natural causes, especially from heart disease, was significantly excessive among women, while death from accidents and suicides was excessive for both men and women. The overall SMR was 1.65 (P < 0.001). Most importantly, we found that the greatest excess of mortality occurred within the first 2 years following hospital discharge. Thus, we were able to demonstrate that risk of mortality in general, and of suicide specifically, differed according to age, gender, diagnosis, and portion of the follow-up. We have subsequently used this method to investigate specific risk factors associated with mortality in mood disorders, schizophrenia, and antisocial personality disorder. Findings from these studies are reported.