Global burden, risk factors, and projections of early-onset dementia: Insights from the Global Burden of Disease Study 2021

Background: Despite increasing global awareness of dementia, reliable estimates of the disease burden associated with Early-Onset Dementia (EOD) remain insufficiently quantified. This study aims to estimate the disease burden of EOD, analyze the burden attributable to risk factors from 1990 to 2021, and project these trends to 2050 at global, regional, and national levels, providing essential data to inform public health policy. Methods: By utilising data from the GBD 2021 database, this study analysed metrics such as age-standardized prevalence (ASPR), mortality (ASMR), and disability-adjusted life years (AS-DALYs) for EOD. Joinpoint Regression analysis was used to calculated average annual percent changes (AAPCs) of ASPR, ASMR, and ASDALYs. Then, the disease burden attributable to high fasting plasma glucose (FPG), high body-mass index (BMI), and tobacco were also reported. Finally, the Bayesian age-period-cohort (BAPC) model was employed to project global ASPR, ASMR and AS-DALYs, as well as ASMR and AS-DALYs attributed to the three risk factors from 2022 to 2050. Results: In 2021, the global case numbers of prevalence, mortality and DALYs for EOD were 7.75 (95 %UI: 5.82, 10.08) million, 73,386 (14,059, 232,169), and 3.77 (1.69, 8.88) million. Despite large increases in case numbers, AAPCs of ASR (0.08 % [0.02, 0.14], 0.07 % [0.05, 0.1], and 0.08 % [0.05, 0.1]) kept stable. Females exhibited higher case numbers and ASR across all disease burden indicators than males. Region- and country-level geographical heterogeneities were evident. Furthermore, global ASMR and AS-DALYs associated with high BMI and high FPG showed a steady increase, while the growth in ASMR and AS-DALYs attributable to tobacco has declined. To 2050, global case numbers of prevalence, mortality and DALYs for EOD will continue to rise, but ASRs won't change considerably. Females are anticipated to remain at a higher risk. The disease burden associated with high BMI and high FPG are expected to persist in their upward trends, whereas that related to tobacco are projected to decline. Conclusion: The increasing burden of EOD underscores the critical need for tailored public health strategies and policies, a unique challenge underrecognized before.