Hardly any Indigenous people in the Amazon rainforest get Alzheimer’s disease and the reasons might help protect us, according to new research. Only about one percent of older individuals are affected — less than anywhere else on Earth.
Alzheimer’s disease rates are up to eleven times higher in western countries such as the U.S. and the U.K. It adds to evidence healthier pre-industrial lifestyles are protective, say scientists at the University of Southern California.
Just six cases were identified among 604 Tsimane and Moseten indians aged 60 and over. They live in the Bolivian Amazon.
“Something about the pre-industrial subsistence lifestyle appears to protect older Tsimane and Moseten from dementia,” says lead author Margaret Gatz, a professor of psychology, gerontology and preventive medicine at USC’s Center for Economic and Social Research, in a statement.
A recent study estimated that people living with dementia globally is set to triple to more than 150 million by 2050. With no cure in sight there is an increasing focus on reducing the risk of developing it.
A closer look at the Tsimane and Moseten tribes
For this latest research on Tsimane and Moseten individuals, an international team, including trained translators and Bolivian doctors, diagnosed dementia and cognitive impairment among the two tribes. They used CT (computed tomography) brain scans, cognitive and neurological assessments and culturally appropriate questionnaires.
Only five cases of dementia were found among the 435 Tsimanes and one among the 169 Mosetens. The roughly 17,000 Tsimane remain physically very active throughout their lifespans as they fish, hunt and farm with hand tools and gather food from the forest.
The 3,000 Moseten also reside in rural villages and engage in subsistence agricultural work. Unlike the more isolated Tsimane, they live closer to towns and have schools, access to clean water and medical services, and are more likely to be literate.
Not all Indigenous tribes boast extraordinary brain health
The study authors compared their results to a systematic review of 15 studies of Indigenous populations in Australia, North America, Guam and Brazil. That found dementia prevalence ranging from 0.5% to 20% among indigenous older adults.
The fact that Indigenous populations in other parts of the world have high rates of dementia may be due to a higher amount of contact with non-Indigenous neighbors. Adoption of modern lifestyles has also led to greater risks of diabetes, hypertension, alcohol abuse, obesity and cardiovascular disease.
Yet these dementia risk factors are extremely low among the Tsimane and Moseten populations.
Previous research has found the Tsimane people have extraordinarily healthy hearts in older age. They have the lowest prevalence of hardening of the arteries known to science. Known medically as coronary atherosclerosis, it is caused by a build up of blood fats that can lead to clots and a stroke or heart attack.
Another recent study showed the Tsimane experience less loss of the brain’s grey matter than their American and European peers. In contrast, lifestyle factors in higher-income countries – including lack of physical activity and diets rich in sugars and fats – contribute to heart disease and may also accelerate brain ageing.
Stopping Alzheimer’s disease
Aging is the most important known risk factor for dementia. But others are modifiable, say the researchers. They include low formal education, midlife hypertension and diabetes, cardiovascular diseases, physical inactivity and air pollution.
Co-author Professor Hillard Kaplan, of Chapman University in orange, California, has studied the Tsimane for two decades. “We’re in a race for solutions to the growing prevalence of Alzheimer’s disease and related dementias,” he says. “Looking at these diverse populations augments and accelerates our understanding of these diseases and generate new insights.”
The Amazon is the largest tropical rainforest on Earth. It covers some 40% of the South American continent. It includes parts of eight countries: Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Guyana, and Suriname.
It is home to 20 million people, who use the wood, cut down trees for farms and for cattle.
“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,” adds co-author Prof Benjamin Trumble, of Arizona State University. “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.”
The study is published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
Article by South West News Service writer Mark Waghorn.