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Original Investigation
July 19, 2021

Global Prevalence of Young-Onset Dementia: A Systematic Review and Meta-analysis

Author Affiliations
  • 1Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Alzheimer Centre Limburg, Maastricht University, Maastricht, the Netherlands
  • 2Department of Primary and Community Care, Radboud University Medical Center, Radboud, the Netherlands
  • 3Groenhuysen, Center for Specialized Geriatric Care, Roosendaal, the Netherlands
  • 4Radboudumc Alzheimer Center, Nijmegen, the Netherlands
  • 5Department of Neurology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC (University Medical Center), Amsterdam, the Netherlands
  • 6Department of Epidemiology and Data Science, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, the Netherlands
  • 7Department of Neurology, Erasmus University Medical Center, Rotterdam, the Netherlands
JAMA Neurol. 2021;78(9):1080-1090. doi:10.1001/jamaneurol.2021.2161
Key Points

Question  What is the global prevalence of young-onset dementia?

Findings  In this systematic review, a total of 95 studies were included, of which 74 studies with 2 760 379 unique patients were included in the meta-analysis; the global age-standardized prevalence of young-onset dementia was 119.0 per 100 000 population aged 30 to 64 years. Estimates increased from 1.1 per 100 000 population aged 30 to 34 years to 77.4 per 100 000 population aged 60 to 64 years.

Meaning  These prevalence estimates show the importance of young-onset dementia worldwide; policy makers could use this information to organize sufficient health care for young people living with dementia.

Abstract

Importance  Reliable prevalence estimates are lacking for young-onset dementia (YOD), in which symptoms of dementia start before the age of 65 years. Such estimates are needed for policy makers to organize appropriate health care.

Objective  To determine the global prevalence of YOD.

Data Sources  The PubMed, Embase, CINAHL, and PsycInfo databases were systematically searched for population-based studies on the prevalence of YOD published between January 1, 1990, and March 31, 2020.

Study Selection  Studies containing data on the prevalence of dementia in individuals younger than 65 years were screened by 2 researchers for inclusion in a systematic review and meta-analysis.

Data Extraction and Synthesis  Prevalence estimates on 5-year age bands, from 30 to 34 years to 60 to 64 years, were extracted. Random-effects meta-analyses were conducted to pool prevalence estimates. Results were age standardized for the World Standard Population. Heterogeneity was assessed by subgroup analyses for sex, dementia subtype, study design, and economic status based on the World Bank classification and by meta-regression.

Main Outcomes and Measures  Prevalence estimates of YOD for 5-year age bands.

Results  A total of 95 unique studies were included in this systematic review, of which 74 with 2 760 379 unique patients were also included in 5-year age band meta-analyses. Studies were mostly conducted in Europe and in older groups in Asia, North America, and Oceania. Age-standardized prevalence estimates increased from 1.1 per 100 000 population in the group aged 30 to 34 years to 77.4 per 100 000 population in the group aged 60 to 64 years. This gives an overall global age-standardized prevalence of 119.0 per 100 000 population in the age range of 30 to 64 years, corresponding to 3.9 million people aged 30 to 64 years living with YOD in the world. Subgroup analyses showed prevalence between men and women to be similar (crude estimates for men, 216.5 per 100 000 population; for women, 293.1 per 100 000 population), whereas prevalence was lower in high-income countries (crude estimate, 663.9 per 100 000 population) compared with upper–middle-income (crude estimate, 1873.6 per 100 000 population) and lower–middle-income (crude estimate, 764.2 per 100 000 population) countries. Meta-regression showed that age range (P < .001), sample size (P < .001), and study methodology (P = .02) significantly influenced heterogeneity between studies.

Conclusions and Relevance  This systematic review and meta-analysis found an age-standardized prevalence of YOD of 119.0 per 100 000 population, although estimates of the prevalence in low-income countries and younger age ranges remain scarce. These results should help policy makers organize sufficient health care for this subgroup of individuals with dementia.

Study Registration  PROSPERO CRD42019119288

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