Higher prevalence of dementia in patients with schizophrenia: A nationwide population-based study

Abstract

Introduction: This study investigates the prevalence of dementia in patients with and without schizophrenia, with a particular focus on age-specific and sex-specific differences.

Methods: We conducted a population-based study using the National Health Insurance claims database from 2010 to 2013. Using a 10:1 matching ratio, 248,919 patients without schizophrenia and 26,591 patients with schizophrenia were identified based on the ICD-10 code. Patients with dementia were extracted by diagnosis or use of anti-dementia drugs. Conditional logistic regression analyses were performed to evaluate the association between schizophrenia and dementia.

Results: The prevalence of dementia was significantly higher in schizophrenia patients compared with that in matched non-schizophrenia patients (9.9% versus 2.2%, P < 0.0001). After adjusting for Charlson comorbidity index and underlying comorbidities, conditional logistic regression showed that schizophrenia was associated with dementia (adjusted odds ratio [AOR], 4.7; 95% confidence interval [CI], 4.4-5.1). When stratified by sex, the AOR was 5.6 (95% CI, 5.0-6.2) among women and 4.0 (95% CI, 3.6-4.5) among men. Moreover, the association between dementia and schizophrenia was strong in elderly patients. The AOR of dementia prevalence was 6.6 (95% CI, 6.1-7.2) in patients aged ≥65 years and 3.4 (95% CI, 3.0-3.8) in patients aged <65 years.

Discussion: Schizophrenia patients were more likely to have dementia compared with non-schizophrenia patients. This association seems greater in higher prevalence groups such as women and patients aged ≥65 years. Further investigation on the mechanism is required.

Keywords: claims data; dementia; elderly; schizophrenia; sex.