Global burden of young-onset dementia, from 1990 to 2021: an age-period-cohort analysis from the global burden of disease study 2021.

This study aims to assess the burden of young-onset dementia worldwide, regionally, and nationally during 1990-2021. Prevalence, incidence, mortality, and disability adjusted life years (DALYs) rates were used to estimate burden of the young-onset dementia. The average annual percentage was utilized to evaluate the trends during 1990-2021. Decomposition analysis was performed to explore driving factors behind changes. Age-period-cohort modeling was used to estimate local drift, age, period and cohort effects. Global age standardized prevalence and incidence of dementia among people under 65 years increased from 93.39 and 16.24 per 100,000 persons in 1990 to 96.09 and 17.16 per 100,000 persons in 2021; mortality increased from 0.89 per 100,000 population to 0.91 per 100,000 population; and age standardized DALYs increased from 45.60 per 100,000 persons to 46.78 per 100,000 persons. Countries with a high, high-middle, and middle SDI experienced an upward trend of prevalence and incidence, and the mortality and DALYs of young-onset dementia in countries with a low-middle and low sociodemographic index was a higher level. Smoking, high body-mass index and high fasting plasma glucose levels were main risk factors. Population growth was the largest factor for the increasing young-onset dementia in all regions. Globally, prevalence, incidence, and DALYs rate of young-onset dementia increased with age, period effects showing a decreasing risk and then an increasing risk. Cohort effects of prevalence and DALYs began to decline after the 1950s. Young-onset dementia presents a growing global health challenge in the age, period and cohort across SDI regions, countries.