Margaret Gatz, Wendy J Mack, Daniel Eid Rodriguez, Raul Quispe Gutierrez, Jesus Bani Cuata, Helena C Chui, Ellen E Walters, Daniel K Cummings, Paul L Hooper, Henrik Zetterberg, Caleb E Finch, Benjamin C Trumble, Jonathan Stieglitz, Michael D Gurven, Randall C Thompson, Gregory S Thomas, HORUS Team, Tsimane Health and Life History Project, Hillard S Kaplan
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.
INTRODUCTION: 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.