Schizophrenia and delusional disorder in older age: community prevalence, incidence, comorbidity, and outcome

The opportunity to assess prevalence, incidence, and outcome of schizophrenia and delusional disorder was provided by an age- and sex-stratified random sample of 5,222 persons age 65 years and over. This sample was chosen from general practitioner lists, and interviewed by psychiatric nurses trained to use the Geriatric Mental State (GMS)-AGECAT computerized diagnostic system. GMS-AGECAT ensured the reliability of the selection of cases between the two waves of the study. A subsample was interviewed by a research psychiatrist. The sample was followed up 2 years later using the same method by interviewers blind to the initial findings. The protocols of all nominated cases and subcases of schizophrenia/paranoid disorder diagnosed by AGECAT were reviewed by a clinician and DSM-III-R diagnoses were made. Refusal rate was 13 percent for initial interviews (wave 1) and 15 percent for reinterview 2 years later (wave 2). The prevalence of DSM-III-R schizophrenia was 0.12 percent (95% confidence interval [CI] 0.04-0.25) and delusional disorder 0.04 percent (95% CI 0.00-0.14). The minimum incidence of schizophrenia for new cases was 3.0 (95% CI 0.00 to 110.70); for new and relapsed cases, 45.0 (95% CI 3.54-186.20); and for delusional disorder, 15.6 (95% CI 0.02-135.10) per 100,000 per year. Two of the five cases with schizophrenia were known to have been first diagnosed before age 65. After 2 years, none of the cases of schizophrenia had recovered fully, but none was deluded at followup. Two had developed dementia. The outcome was bad because they remained cases of some type of psychiatric illness but good because of the improvement in their schizophrenia/delusion disorder symptoms.