Scientists looking for a way to fight Alzheimer’s have found valuable clues on how to tackle the memory-destroying condition in the Amazon rainforest.
Researchers have identified a tribe living in the Bolivian Amazon whose brain volume decreases about 70% slower than Westerners as they age.
Researchers say that the healthy diet and active lifestyle of the Tsimane people of the Bolivian Amazon could explain this huge difference.
Brain atrophy – or loss of brain cells – is a symptom associated with Alzheimer’s disease and dementia.
While brain scans show the Tsimane have similar levels of brain inflammation – a symptom seen as a sign of mental breakdown – their brains remain healthier.
The researchers behind this discovery believe that because they lack access to modern medicine like their European counterparts, their diet and lifestyle are the most likely explanation.
The Tsimane are extremely physically active and eat a diet high in fiber, including vegetables, fish and lean meat.
Previous research has also shown that members of the tribe have a very low risk of heart disease compared to Europeans.
The results were published in Journal of Gerontology, Series A: Biological Sciences and Medical Sciences.
The new study was led by Dr. Hillard Kaplan, professor of health economics and anthropology at Chapman University in the United States, who has studied Tsimane for nearly two decades.
He said: “Our sedentary lifestyle and our diet high in sugars and fats can accelerate the loss of brain tissue with age and make us more vulnerable to diseases such as Alzheimer’s disease.
“Tsimane can serve as a basis for healthy cerebral aging.
“This study shows that the Tsimane stand out not only in terms of heart health, but also in terms of brain health.
“The results suggest many possibilities for interventions to improve brain health, even in populations with high levels of inflammation.”
The researchers scanned the brains of 746 Tsimane adults aged 40 to 94.
Many study participants had to travel from isolated villages to Trinidad, Bolivia, the nearest town with CT scans. This trip could last up to two full days with river and road trips.
The team used the scans to calculate brain volumes, then looked at their association with age for Tsimane.
Then, they compared these results to those of three industrialized populations in the United States and Europe.
Scientists have found that the difference in brain volume between middle age and old age is 70% smaller in Tsimane than in Western populations.
This, the researchers say, suggests that Tsimane’s brains likely experience much less brain atrophy than Westerners as they age – atrophy is correlated with risk for cognitive impairment, functional decline, and dementia.
The researchers noted that the Tsimane have high levels of inflammation, which is generally associated with brain atrophy in Westerners.
However, this high inflammation does not have a pronounced effect on the Tsimane brain.
According to the study’s authors, Tsimane’s low risk of heart disease may outweigh his inflammatory risk from the infection, raising new questions about the causes of dementia.
One possible reason is that in Westerners inflammation is associated with obesity and metabolic causes while in Tsimane it is caused by respiratory, gastrointestinal and parasitic infections.
Infectious diseases are the leading cause of death among the Tsimane, the researchers explained.
University of Southern California researcher Dr Andrei Irimia said: “The Tsimane have provided us with amazing natural experience on the potentially damaging effects of modern lifestyles on our health.
“These results suggest that brain atrophy can be significantly slowed down by the same lifestyle factors associated with a very low risk of heart disease.”
The indigenous Tsimane people came to the attention of scientists when an earlier study found that they had extraordinarily healthy hearts at an older age.
This earlier study, published by The Lancet in 2017, showed that Tsimane had the lowest prevalence of coronary atherosclerosis of any population known to science and that she had few risk factors for cardiovascular disease.
The very low rate of heart disease among the estimated 16,000 Tsimane is most likely related to their pre-industrial subsistence lifestyle of hunting, gathering, fishing and farming.