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Global Incidence of All-Cause Dementia: A Meta-Analysis
Ashleigh S Vella1, Rachel Visontay2, Darren M Lipnicki1
1Centre for Healthy Brain Ageing, Discipline of Psychiatry & Mental Health, School of Clinical Medicine, University of New South Wales, Sydney, New South Wales, Australia.
Importance:
Global dementia incidence estimates are limited by underrepresentation of low- and middle-income countries and heterogeneous analytic methods. Due to these limitations, true understanding of the global dementia landscape remains incomplete.
Objective:
To identify dementia incidence rates by age and sex in various regions worldwide (high-income countries and low- and middle-income countries) where data on clinically based dementia diagnoses were available.
Data Sources:
Retrospective community-based cohorts from the Cohort Studies of Memory in an International Consortium (COSMIC); baseline recruitment commenced between January 1990 and December 2011 and follow-up data were collected through the end of 2021. Data were analyzed from June 2024 to June 2025.
Study Selection:
Eligible studies included longitudinal COSMIC cohort studies with a clinically based diagnosis of dementia. Individual participant-level data from 22 population-based longitudinal cohorts (N = 38 418) spanning 18 countries or territories across 6 continents were included.
Data Extraction And Synthesis:
Data extraction and assessment of study quality and validity were conducted according to Meta-Analyses of Observational Studies in Epidemiology (MOOSE) guidelines. Individual participant-level data were meta-analyzed in a 2-step process using random intercepts for country and study at the global and regional levels and by country income level.
Main Outcomes And Measures:
For each study with a clinically based diagnosis, incidence rates for all-cause dementia were calculated and a 2-step meta-analysis was conducted. Using a person-years at risk framework with inverse-probability censoring weights and Poisson models, age- and sex-specific incidence were estimated and then standardized to the 2023 global age-sex population structure.
Results:
Across 287 632 person-years at risk, 3001 participants developed dementia. Age- and sex-standardized incidence was 9.7 (95% CI, 7.89-11.97) per 1000 person-years at risk. Age-standardized incidence was higher in women than men (10.6; 95% CI, 8.61-13.11 vs 8.6; 95% CI, 6.94-10.72). Standardized incidence was higher in low- and middle-income countries (13.6; 95% CI, 9.67-19.24) than in high-income countries (8.3; 95% CI, 6.57-10.54). Applying age- and sex-specific rates to the projected 2050 population yielded a projected 24.7 million new cases, assuming constant incidence over time.
Conclusions And Relevance:
The harmonized estimates presented in this study provide a comparable benchmark for global dementia incidence and inform planning for prevention, diagnosis, and memory-care services, particularly in underrepresented low- and middle-income country settings.