Low dementia prevalence in Amazonian communities may reflect shorter survival, not lower incidence

What the research found

Study (longitudinal). Margaret Gatz, Hillard Kaplan and colleagues report in Alzheimer’s & Dementia (doi 10.1002/alz.71750) on 730 Tsimané and Mosetén adults in the Bolivian Amazon without dementia at first assessment, revisited nearly five years later. They identified 22 new dementia cases (7.40 per 1,000 person-years); follow-up prevalence stayed below 2%. Incidence was not dramatically lower than U.S. and northern European figures, especially under age 80. People with dementia had more than six times the mortality of those with normal cognition, and survival after diagnosis appeared two to three times shorter than in U.S. studies. Cognitive pattern leaned toward attention and task-management more than memory; blood work associated cases with neurofilament light, not amyloid or phosphorylated tau typical of Alzheimer’s. Twenty-two cases are too few to settle lifestyle versus genetics. Educational brain-aging notes, not a diagnosis.

Evidence level: Human study. A study in people, but an association isn't proof of cause.

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