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

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.

The prevalence and associated demographic factors of dementia from a cross-sectional community survey in Kingston, Jamaica.

OBJECTIVES: Using a cross-sectional community survey, the authors aimed to estimate the prevalence of dementia among a sample of older Jamaicans and to identify associated demographic factors. METHODS: From February to July 2010, persons of age ≥60 years were randomly selected from two communities in Kingston, Jamaica and screened with the Mini Mental Status Examination (MMSE). All MMSE-positive participants and an equal number of matched MMSE-negative participants underwent definitive diagnostic evaluation for dementia using the Clinical and Diagnostic Assessment Procedure for Dementia. Subsequently derived MMSE sensitivity and specificity measures from the subsample were used to estimate the overall prevalence of dementia (primary outcome). Chi square, Fisher's Exact, Exact, Spearman's correlation and t-tests were used to explore associations of dementia with age, gender, educational level and socioeconomic status. Statistical significance was taken as p < 0.05. RESULTS: Two hundred participants were recruited. Age-standardized prevalence rates of dementia were 5.07% (standardized to the Jamaican population) and 5.32% (standardized to the West Europe population). Dementia was more prevalent among older persons (Spearman's rho = 0.31; p < 0.001); no other significant associations were found. CONCLUSIONS: Dementia prevalence found in this study is lower than figures from previous Caribbean reports. The older persons are disproportionately affected.