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Amazonian Indigenous Groups Have World's Lowest Rate of Dementia

By: April Carson

A new study published in The Lancet found that two indigenous groups in the Bolivian Amazon had among the world's lowest dementia rates, highlighting how important it is for scientists around the globe to focus on Alzheimer's disease.

The study looked at three indigenous groups in Bolivia: the Tsimane, who live a traditional lifestyle and have a diet high in fresh fruits and vegetables; the Yucpa, who are hunter-gatherers; and the Chiquitano, who are cattle ranchers. While the dementia rates for all three groups were low, the Tsimane had the lowest rate, with only 2.2 cases of dementia per 1,000 people aged 65 and over.

Only about 1% of older Tsimane and Moseten people suffer from dementia, according to a study conducted by an international team. In contrast, 11% of persons age 65 and over in the United States had dementia, according to the Alzheimer's Association.

“Our research suggests that the pre-industrial subsistence lifestyle has a protective effect against dementia in Tsimane and Moseten people,” said Margaret Gatz, the lead study author and professor of psychology, gerontology and preventive medicine at USC Dornsife's Center for Economic and Social Research.

To diagnose dementia and cognitive impairment among the Tsimane and Moseten, researchers used computed tomography (CT) brain scan pictures, cognitive and neurological tests, and culturally appropriate questionnaires — aided by a local team of linguists and Bolivian doctors — to identify dementia and cognitive impairment.

The research, published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, revealed just five cases of dementia among 435 Tsimane people and only one case among 169 Moseten elders aged 60 and over.

In the same elderly groups, 8% of Tsimane and 10% of Moseten were diagnosed with moderate cognitive impairment (MCI), which is characterized by early-stage memory loss or deterioration in other cognitive abilities such as language or spatial perception. The study's authors remarked that these rates are comparable to MCI observed in high-income countries like the United States.

The researchers were taken aback to discover that the study participants with dementia or MCI had unusually large calcifications of their intracranial arteries. During neurological testing, these individuals frequently manifested Parkinsonian symptoms and attention, spatial awareness, and executive function deficits.

Researchers discovered these vascular calcifications in the CT scans of those without dementia or MCI, as well as those with cognitive impairment. They add that there is still need for additional study regarding the influence of vascular components, as well as infectious and inflammatory diseases - which are prevalent in these groups - and other risks for dementia. To this end, the research team will be returning to all Tsimane and Moseten villages to re-examine those previously examined later this year.

The Comparison

The 17,000 Tsimane who remain physically active throughout their lifespans as they fish and hunt with hand tools or farm in the forest. The Moseten are a small tribe that lives in rural areas, farms and engages in subsistence agriculture; unlike the isolated group, they live closer to towns, have access to clean water, and healthcare. They are more likely to be educated.

The researchers compared their findings to a comprehensive review of 15 research involving indigenous people in Australia, the United States, Guam, and Brazil. Among indigenous older persons, dementia incidence varied from 0.5% to 20%.

The high rate of dementia among indigenous communities in other parts of the world could be attributed to more interaction with — and adoption of customs from — their non-indigenous neighbors. They also face greater risks of diabetes, hypertension, alcohol abuse, obesity, and heart disease.

The Tsimane and Moseten people have extremely low rates of dementia. The Tsimane have the healthiest hearts of any population studied, with the lowest incidence of coronary atherosclerosis (a disease manifested as fatty deposits in the arteries) of any known group, according to previous research published in The Lancet. This difference may be attributed to their lifestyle as hunters-gatherers.

The Tsimane, according to a new study published in Nature Communications, have less brain atrophy than their American and European counterparts. According to another research published last year in The Gerontology Journal of America — led by USC assistant professor Andrei Irimia, also a co-author on the current paper — the Tsimane experience less brain atrophy than their peers from across the world.

According to the study, lifestyle factors in richer nations — particularly lack of exercise and high-sugar and fat diets — contribute to heart disease and may also accelerate brain aging, in contrast to the Tsimane.

Alzheimer’s Research

The most significant known risk factor for Alzheimer's and other dementia is age. Low formal education, midlife hypertension and diabetes, heart disease, inactivity, and — most recently — air pollution have all been linked to increased dementia and Alzheimer's disease incidence.

According to projections, the worldwide population with Alzheimer's disease will almost triple by 2050, to more than 152 million people.

“We're in a race against time to find treatments for the growing incidence of Alzheimer's and other dementia diseases,” noted Hillard Kaplan, a study co-author and professor of health economics and anthropology at Chapman University who has studied the Tsimane for two decades. “Analyzing these diverse groups adds to our knowledge of these illnesses and helps us make new discoveries.

Benjamin Trumble, a study author and an associate professor in Arizona State University's School of Human Evolution and Social Change, the Center for Evolution and Medicine, added: “Working with populations like the Tsimane and Moseten may help us better understand global human variation and what health was like in different environments before industrialization. What we do know is that being sedentary, urban, industrial is rather new when compared to how our forefathers lived for almost 99% of human history.”

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About the Blogger:

April Carson is the daughter of Billy Carson. She received her bachelor's degree in Social Sciences from Jacksonville University, where she was also on the Women's Basketball team. She now has a successful clothing company that specializes in organic baby clothes and other items. Take a look at their most popular fall fashions on

To read more of April's blogs, check out her website! She publishes new blogs on a daily basis, including the most helpful mommy advice and baby care tips! Follow on IG @bossbabymav



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