Amazonian Tribes with Low Rates of Dementia May Hold Clues to Prevention

There are an estimated seven million American adults over the age of 65 living with some type of dementia. That accounts for about 13% of this age group. In contrast, researchers have discovered that two Amazonian tribes have some of the lowest dementia rates in the world, and there’s hope that investigating why may help with prevention elsewhere.

The Tsimane and Moseten indigenous groups, who live in the Bolivian Amazon, were recently discovered to have a roughly 1% rate of dementia among older community members. The international research team involved in the study, which was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, says the tribes’ pre-industrial subsistence lifestyle may play a role and studying how they live could hold answers for other aging populations.


Dr. Benjamin Trumble, study co-author and associate professor at Arizona State University, explains, “By working with populations like the Tsimane and the Moseten, we can get a better understanding of global human variation and what human health was like in different environments before industrialization. What we do know is the sedentary, urban, industrial life is quite novel when compared with how our ancestors lived for more than 99% of humanity’s existence.”

In contrast to many urban and industrial cultures, the Tsimane – who number about 17,000 – have a more active life. They fish, hunt, farm with hand tools, and gather food from the forest throughout their lifetimes. Past research has shown that they have the lowest reported rate of coronary artery disease in the world and lower rates of brain atrophy than Americans and Europeans. They are also relatively isolated.

The Moseten – who have a population around 3,000 – live closer to towns, have schools, and are more apt to be literate. They, too, however, live a life with subsistence agricultural work.


To measure dementia prevalence among these groups, researchers used CT brain scans, cognitive and neurological tests, and culturally appropriate questionnaires. They found that of the 435 Tsimane adults 60 and older who were evaluated, only five had dementia. Additionally, there was only one case detected in 169 Moseten adults in the same age group.

However, both demonstrated higher rates of mild cognitive impairment: 8% of the Tsimane group and 10% of the Moseten. These figures are more in line with those observed in high-income countries including the United States.

The team says that heart disease and accelerated brain aging are linked with the less active lifestyles and unhealthy diets found in many high-income countries. These two tribes don’t fall into the same pattern, so that could play a role in their relative resilience to dementia. Regardless, further study into their brain health may help lower dementia rates elsewhere.


Dr. Hillard Kaplan, study co-author and professor of health economics and anthropology at Chapman University, says, “We’re in a race for solutions to the growing prevalence of Alzheimer’s disease and related dementias. Looking at these diverse populations augments and accelerates our understanding of these diseases and generate new insights.”

This research could have implications for millions of people, as it is currently estimated that more than 150 million people worldwide will have dementia by 2050.

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