Although people in industrialized nations have access to modern health care, they are more sedentary and eat a diet high in saturated fat. In contrast, the Tsimane have little to no access to medical care, but are extremely physically active and consume a high-fiber diet that includes vegetables, fish, and lean meat.
“The Tsimanes have provided us with an amazing natural experiment on the potentially damaging effects of modern lifestyles on our health,” said study author Andrei Irimia, assistant professor of gerontology, neuroscience and biomedical engineering at the Leonard School of Gerontology. Davis from USC and the USC Viterbi School of Engineering. “These findings suggest that brain atrophy can be substantially reduced by the same lifestyle factors associated with a very low risk of heart disease.”
The researchers enrolled 746 Tsimane adults, ages 40 to 94, in their study. To purchase brain scans, they provided transportation for participants from their remote villages to Trinidad, Bolivia, the nearest city with CT scanning equipment. That trip could take up to two full days with road and river trips.
The team used the scans to calculate brain volumes and then examined their association with age for Tsimane. They then compared these results with those of three industrialized populations in the US and Europe.
The scientists found that the difference in brain volumes between middle age and old age is 70% less in Tsimane than in Western populations. This suggests that Tsimane’s brains likely experience much less brain atrophy than Westerners as they age; atrophy is correlated with the risk of cognitive impairment, functional impairment, and dementia.
Researchers point out in his study, published in The Journals of Gerontology last month, that the Tsimane have high levels of inflammation, which is generally associated with brain atrophy in Westerners. But their study suggests that high inflammation does not have a pronounced effect on Tsimane’s brains.
According to the study authors, Tsimane’s low cardiovascular risks may outweigh the inflammatory risk caused by 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 driven by respiratory, gastrointestinal, and parasitic infections. Infectious diseases are the leading cause of death among the Tsimane.
“Our sedentary lifestyles and a diet rich in sugar and fat may be accelerating the loss of brain tissue with age and making us more vulnerable to diseases such as Alzheimer’s,” said study author Hillard Kaplan, professor of health economics. and anthropology at Chapman University, who has studied the Tsimane for nearly two decades. “Tsimane can serve as the foundation for healthy brain aging.”
Healthier hearts and healthier brains
The Tsimane indigenous people captured the attention of scientists – and the world – when a previous study found that they had remarkably healthy hearts in old age.
That earlier study, published by The Lancet in 2017, showed that Tsimane has the lowest prevalence of coronary atherosclerosis of any population known to science and that they have few risk factors for cardiovascular disease. The very low rate of heart disease among the roughly 16,000 tsimanes is most likely related to their pre-industrial subsistence lifestyle of hunting, gathering, fishing and farming.
“This study shows that the Tsimane stand out not only in terms of heart health, but brain health as well,” Kaplan said. “The findings suggest broad opportunities for interventions to improve brain health, even in populations with high levels of inflammation.”
Fountain: University of South Carolina
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