Prevalence and Incidence of Dementia for Schizophrenia and Other Primary Psychotic Disorders: A Systematic Review and Meta‐Analysis

ABSTRACT

People with psychotic disorders have higher dementia risk. This study aimed to investigate the prevalence and incidence of dementia in this population. Data were synthesized through meta‐analysis (including subgroup and sensitivity analyses) and narrative synthesis. The pooled dementia prevalence was 24.3% (95% CI: 20.5%–28.5%, I ²  = 84.7%, p < 0.001) in older adults after excluding one outlier. Factors contributing to heterogeneity included prevalence types, settings, geographical regions, and age. The dementia incidence varied widely. This review identified elevated but heterogeneous dementia rates in psychotic disorders, calling for more population‐based studies to provide evidence for integrated service planning.

1. Introduction

Primary psychotic disorders comprise schizophrenia (SCZ) and related psychotic disorders. More than 70% of people with SCZ exhibit cognitive impairment, which contributes to impaired functional outcomes (Goonathilake et al. 2022). Accumulating evidence has shown that SCZ and other primary psychotic disorders are associated with higher risk of dementia at an earlier age compared to their healthy age peers (Miniawi et al. 2022; Park et al. 2025).

Dementia is characterized by progressive cognitive decline (Livingston et al. 2024). Dementia prevalence remains low in midlife, with estimates reporting 6.3 per 100 000 population aged 45–49 years, and increases with age, reaching 77.4 per 100 000 in those aged 60–64 years (Hendriks et al. 2021). SCZ and dementia both remain within the top 25 causes of years lived with disability worldwide (GBD 2021 Diseases and Injuries Collaborators 2024). With the comorbidity, the patients' life quality is deteriorating. In order to promote evidence‐based service planning, clinicians need to know how many patients with psychotic disorders are likely to have dementia. However, the epidemiology of dementia remains unclear, with prevalence estimates ranging from 14.7% to 28.6% in recent studies and differing substantially across settings and study design (Baudouin et al. 2025; Park et al. 2025; Stewart et al. 2022).

A preliminary search in PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and China National Knowledge Infrastructure (CNKI) database revealed several systematic reviews focusing on the association between psychotic disorders and dementia risk rather than absolute prevalence and incidence estimates (Cai and Huang 2018; Miniawi et al. 2022; Stafford et al. 2022). With the growing number of original studies, a comprehensive synthesis is needed to provide prevalence measures to inform resource allocation and incidence estimates for proactive service planning. Therefore, we conducted a systematic review to synthesize evidence on the prevalence, cumulative incidence, and incidence rate of dementia in this population.

2. Methods

The present study followed the Preferred Reporting Items for Systematic Reviews and Meta‐analysis (PRISMA) (Page et al. 2021) and a pre‐registered protocol (International Prospective Register of Systematic Reviews, PROSPERO: CRD42024543882).

2.1. Search Strategy and Eligibility Criteria

We included observational studies that investigated dementia prevalence or incidence in people with psychotic disorders. Search strategy and eligibility criteria were provided in Supplementary Methods and Table S1.

2.2. Screening, Data Extraction and Quality Appraisal

Screening, data extraction, and quality appraisal were conducted by at least two reviewers independently, and quality was assessed with the Newcastle‐Ottawa Quality Assessment Scale (Wells et al. 2000) (see Supplementary Methods and Table S2 for details).

2.3. Statistical Analyses

The prevalence, incidence, and corresponding 95% confidence intervals (CIs) were calculated if proportions were not reported directly (methods of calculation seen in Table S3). Given the substantial influence of age on dementia prevalence, pooled prevalence was estimated separately for two subgroups: studies including all‐age participants and studies with a minimum participant age of 45 years. The selected age threshold was lower than conventional threshold for older adults, given the 10–15 years' reduction in life expectancy associated with psychotic disorders (Chan et al. 2023). The data of incidence and dementia subtypes were summarized narratively, because meta‐analysis was inappropriate for few studies with high clinical and methodological heterogeneity (Higgins et al. 2023).

Prevalence estimates were synthesized using random‐effect meta‐analysis models (Urso et al. 2025). Details on pooled prevalence estimates and 95% CIs, heterogeneity analysis, post hoc subgroup analyses, and sensitivity analysis were provided in Supplementary Methods.

3. Results

3.1. Study Selection and Characteristics

Twenty‐nine studies (n = 576 727) met the inclusion criteria. Twelve were included in the meta‐analysis, and 17 were synthesized narratively (study selection and reference details seen in Figure S1 and Table S4). Studies were conducted in Europe, the United States, Canada, Australia, South Korea, Israel and China (study characteristics presented in Tables S5–S8).

Methodologically, 40% of the prevalence studies and over 80% of the incidence studies were rated as high quality (Tables S9 and S10). Reporting of CIs and attrition rates was notably insufficient across the literature.

3.2. Prevalence of Dementia

Twelve studies (n = 193 967) reported dementia prevalence. The meta‐analysis of four studies including individuals of all ages (n = 73 367) revealed a pooled prevalence of 9.4% (95% CI: 4.0% – 20.5%, I ² = 99.3%). The meta‐analysis of eight studies of older adults (n = 120 600) drew a pooled prevalence of 27.2% (95% CI: 17.6% – 39.4%) (Figure 1a), with high heterogeneity (I ² = 98.4%, Q = 443.58, τ ² = 0.413, p < 0.001, prediction interval [PI] = 6.9% – 65.3%). In leave‐one‐out sensitivity analysis, one study based on an urban safety net healthcare system that deviated significantly from the general study pool was identified as an outlier (Hendrie et al. 2014) (Table S11). Excluding the outlier led to a notable reduction in heterogeneity (I ² = 84.7%, Q = 39.11, τ ² = 0.029, p < 0.001, PI = 16.7% – 33.9%), and the pooled prevalence from seven studies (n = 119 843) was 24.3% (95% CI: 20.5% – 28.5%) (Figure 1b).

FIGURE 1.

(a) Random effects meta‐analysis (n = 12) for pooled prevalence of dementia in people with primary psychotic disorders. (b) Sensitivity analysis (n = 11), excluding Hendrie et al. (2014).

Exploratory subgroup analyses after outlier exclusion revealed significantly higher prevalence in the following groups: older vs. younger adults, non‐European vs. European regions, population‐based vs. hospital‐based studies, and point prevalence vs. period prevalence (Table S12). Results of subgroup analyses without outlier exclusion were in Table S13.

3.3. Incidence of Dementia

Nineteen studies (n = 501 118) reported incidence with follow‐up years spanning 4 to 50 years. Cumulative incidence was 1.7%–21.5% in population‐based studies. The incidence rate, measured by eight studies, varied from 1.72 to 77.40 per 1000 person‐year.

3.4. Dementia Subtypes

Among studies on prevalence, Alzheimer's disease was the most frequently reported cause, with prevalence ranging from 7.8% to 12.2% in population‐based studies, followed by vascular dementia (2%–5%). Four of five studies on incidence identified unspecified dementia as the most common subtype (Table S14).

4. Discussion

This systematic review synthesized worldwide evidence on dementia epidemiology in psychotic disorders. The pooled dementia prevalence estimate was 24.3% (95% CI: 20.5%–28.5%) in older individuals with psychotic disorders. Despite high heterogeneity, the PI (16.7%–33.9%) remained far above the estimated dementia prevalence in the general older population (Cao et al. 2020).

Estimates varied by demographics and methodology. Consistent with prior literature, higher prevalence was associated with older age and non‐European regions (Ku et al. 2016; Miniawi et al. 2022). Population‐based studies yielded higher estimates than hospital‐based studies, likely reflecting selection bias as community surveys better capture patients in nursing homes (Henni Rached and Ullmer 2025). Point prevalence estimates exceeded period prevalence, likely because active screening protocols in point‐prevalence studies detect undiagnosed cases better than retrospective follow‐ups.

Current literature relies primarily on developed countries. Synthesizing incidence data is challenging, because most studies report crude cumulative incidence rather than standardized incidence rates, and the competing risk of death is rarely addressed (Solmi et al. 2025). Given the large number of affected individuals, dementia screening should be considered. Future research must expand to developing countries, provide prevalence and incidence data stratified by age, sex, and ethnicity, and report standardized incidence rates.

This report has several limitations. High heterogeneity limited the stability of the meta‐analysis results, and the number of studies made it impossible to undertake meta‐regression. While we performed post hoc subgroup analyses, these results should be interpreted with caution.

5. Conclusion

The current literature on dementia epidemiology in psychotic disorders shows elevated dementia prevalence but is limited in numbers and generalizability. Our review calls for high‐quality population‐based studies to determine the prevalence and incidence of dementia and provide more evidence for the reference of service planning.

Funding

This work was supported by the National Natural Science Foundation of China (C.L., grant number 8257055641, 82161138021) (X.C., grant number 82101543); the Feixiang Program of Shanghai Mental Health Center (X.C., grant number 2022‐FX‐04); and the Qingmian Program of Shanghai Mental Health Center (X.C., grant number 2025‐QM01).

Disclosure

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Data S1: Supplementary Methods.

Figure S1: Flow diagram of the study selection process.

Table S1: Search strategy (e.g., PubMed).

Table S2: Definition of extracted study characteristics and outcomes.

Table S3: Methods for calculating prevalence and incidence of dementia.

Table S4: List and references of articles in full‐text screening and reasons for exclusion.

Table S5: Characteristics of included studies on dementia prevalence (n = 12).

Table S6: Characteristics of included studies on dementia incidence (n = 19).

Table S7: Detailed characteristics of included studies on dementia prevalence.

Table S8: Detailed characteristics of included studies on dementia incidence.

Table S9: Quality assessment for cohort studies (n = 23).

Table S10: Quality assessment for cross‐sectional studies (n = 6).

Table S11: Leave‐one‐out analysis for pooled prevalence of dementia in older individuals.

Table S12: Meta‐analysis and subgroup analyses of the prevalence of dementia in older adults (n = 7).

Table S13: Meta‐analysis and subgroup analyses of the prevalence of dementia in older adults (n = 8).

Table S14: Prevalence and incidence of specific subtypes of dementia.

Data Availability Statement

The data that support the findings of this study are available in the Supporting Information.