Incidence of dementia and mild cognitive impairment in two Indigenous Bolivian cohorts

Abstract

We studied dementia incidence and risk factors in Indigenous Tsimane and Moseten Amerindian populations in Amazonian Bolivia with largely subsistence lifestyles. METHODS A median of 4.7 years after baseline dementia assessment, 730 participants (52% male; mean age 67.3 years) were re-visited at two follow-up phases to determine new cases among non-demented at baseline. Clinical evaluation was adapted to culture, language, and illiteracy. RESULTS There were 22 incident dementia cases (7.40/1000 person years; 95% confidence interval = 4.87?11.24). Prevalence rates remained < 2%. Mortality among dementia cases at baseline was significantly greater versus cognitively normal participants. In exploratory analyses, apolipoprotein E ε4 genotype, thoracic aortic calcium, and plasma neurofilament light chain were associated with incident dementia; other risk factors, amyloid, and phosphorylated tau were non-significant. DISCUSSION In these populations, dementia prevalence is strikingly low, reflecting modestly low incidence and shortened life expectancy after diagnosis. Next steps include delineating vascular contributions versus Alzheimer's disease pathology in dementia cases.

Reference

Margaret Gatz, Wendy Mack, Daniel Eid Rodriguez, Raul Quispe Gutierrez, Juana Bani Cuata, Helena Chui, Ellen E. Walters, Daniel Cummings, Paul L. Hooper, Henrik Zetterberg, Caleb Finch, Benjamin C. Trumble, Jonathan Stieglitz, Michael Gurven, Randall C. Thompson, Gregory Thomas, and Hillard Kaplan, “Incidence of dementia and mild cognitive impairment in two Indigenous Bolivian cohorts”, Alzheimer's and Dementia, vol. 22, n. 9 (e71750), September 2026.