Global prevalence of young-onset dementia higher than previously estimated

In a systematic review and meta-analysis of 95 studies, researchers identified a global, age-standardized rate of young-onset dementia of 119 per 100,000 population, which is higher than previous estimates.

The results were published in JAMA Neurology.

“Dementia is generally perceived as a condition that affects older adults, with prevalence estimates of late-onset dementia (LOD) increasing exponentially with age. Approximately 45 million people live with LOD worldwide,” the researchers wrote. “The focus on LOD may marginalize the importance of dementia in younger people. Exact figures on the burden of [young-onset dementia (YOD)] are needed to determine the necessary budget and set priorities by policy makers.”

Stevie Hendriks, MSc, of the department of psychiatry and neuropsychology in the School for Mental Health and Neuroscience, Alzheimer Center Limburg, at Maastricht University in the Netherlands, and colleagues analyzed 95 population-based studies published between Jan. 1, 1990, and March 31, 2020, in the systematic review, of which 74 studies with data on 2,760,379 patients aged 30 to 64 years were also included in the meta-analyses of 5-year age groupings. The researchers included studies on demographic subpopulations, but studies on specific groups at risk for YOD, such as patients with Down syndrome or HIV, were excluded. The studies also included a variety of geographic regions, including Europe, Asia, North America and Oceania.

The researchers reported a global, age-standardized YOD prevalence of 119 per 100,000 people among those aged 30 to 64 years, which Hendriks and colleagues wrote projects to “3.9 million people aged 30 to 64 years living with YOD worldwide” based on the U.N.’s world population information of 2019. Among people aged 30 to 34 years, they reported an increase in prevalence of 1.1 per 100,000 people, while the prevalence among people aged 60 to 64 years was 77.4 per 100,000.

Study results demonstrated that overall YOD prevalence was higher in Europe than in the U.S. (159.4 vs. 114.7 per 100,000 population, respectively) and, in the age group of 60 to 64 years, in upper-middle-income countries. Hendriks and colleagues found that the prevalence in men and women was similar.

For specific diseases, Alzheimer’s disease had the highest global prevalence at 41.1 per 100,000 population. Vascular dementia and frontotemporal dementia followed with rates of 14.9 and 2.3 per 100,000 worldwide, respectively. Data on dementia with Lewy body and Parkinson’s diseases were “too diverse” to be included in the meta-analysis, according to the researchers; 3 studies on alcohol-related dementia reported prevalence estimates of 4.9 to 16.3 per 100,000 among those aged 30 to 64 years.

Limitations included underrepresentation of Africa and low-income countries, upward-biased estimates due to 41 studies reporting data only from 60 to 64 years of age, some small sample sizes and lack of diversity precluding ethnic analysis.

“Based on the available literature, this systematic review and meta-analysis estimated the age-standardized prevalence to be 119 per 100,000 population globally. Although this is higher than previously thought, it is probably an underestimation owing to lack of high-quality data,” Hendriks and colleagues wrote. “This should raise awareness for policymakers and health care professionals to organize more and better care for this subgroup of individuals with dementia.”