A team of international researchers has found that the indigenous Tsimane people of the Bolivian Amazon suffer less brain atrophy than their American and European peers. The decrease in their brain volume with age is 70% slower than in Western populations. Accelerated loss of brain volume can be a sign of dementia.
The study was published Wednesday in The Journal of Gerontology, Series A: Biological Sciences and Medical Sciences.
Although people in industrialized countries have access to modern medical care, they are more sedentary and eat a diet high in saturated fat. In contrast, the Tsimane have little or no access to health care, but are extremely physically active and consume a high-fiber diet that includes vegetables, fish and lean meat.
“The Tsimane have provided us with an amazing natural experience on the potentially harmful effects of modern lifestyles on our health,” said the author of the study. Andrei irimia, Assistant Professor of Gerontology, Neuroscience and Biomedical Engineering at USC Leonard Davis School of Gerontology and USC Viterbi School of Engineering. “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 researchers enrolled 746 Tsimane adults, aged 40 to 94, in their study. To acquire brain scans, they provided transport for participants from their remote villages to Trinidad, Bolivia, the nearest town with CT equipment. 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 suggests that Tsimane brains probably experience much less brain atrophy than Westerners as they age; atrophy is correlated with the risk of cognitive impairment, functional decline and dementia.
The researchers note 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 the Tsimane brain.
Le Tsimane: a healthy heart and – new research shows – healthy brain aging
According to the study authors, Tsimane’s low cardiovascular risks may outweigh its inflammatory risk from infection, raising new questions about the causes of dementia. One possible reason is that, in Westerners, inflammation is associated with obesity and metabolic causes. In Tsimane, however, it is caused by respiratory, gastrointestinal and parasitic infections. Infectious diseases are the main cause of death among the Tsimane.
Tsimane can be used as a basis for healthy brain aging.
“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,” said the author of the study. Hillard Kaplan, a professor of health economics and anthropology at Chapman University who studied Tsimane for nearly two decades. “Tsimane can serve as a basis for healthy brain aging.”
The indigenous Tsimane people came to the attention of scientists – and around the world – when an earlier study found they had extraordinarily healthy hearts at an older age. This earlier study, published by The Lancet in 2017, showed that Tsimane have the lowest prevalence of coronary atherosclerosis of all populations known to science and that they have 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.
“This study demonstrates that the Tsimane stand out not only in terms of heart health, but also brain health,” said Kaplan. “The results suggest many possibilities for interventions to improve brain health, even in populations with high levels of inflammation.”
Besides Irimia and Kaplan, study authors include Nikhil N. Chaudhari, David J. Robles, Kenneth A. Rostowsky, Alexander S. Maher, Nahian F. Chowdhury, Maria Calvillo, Van Ngo, Margaret Gatz, Wendy J. Mack and Caleb E. Finch (USC), E. Meng Law (Monash University), Mr. Linda Sutherland, James D. Sutherland and Gregory S. Thomas (MemorialCare, Fountain Valley, Calif.), Christopher J. Rowan (Renown Regional Medical Center ), L. Samuel Wann (Ascension Healthcare), Adel H. Allam (Al-Al-Alzhar University, Egypt), Randall C. Thompson (St. Luke’s Mid America Heart Institute), David E. Michalik (University of California, Irvine ), Daniel K. Cummings and Edmond Seabright and Paul L. Hooper (University of New Mexico), Sarah Alami and Michael D. Gurven (University of California, Santa Barbara), Angela R. Garcia and Benjamin C. Trumble (Arizona State University, Tempe) and Jonathan Stieglitz (Institute of Advanced Studies, Toulouse, France).
The research funding was provided by the National Institute of Aging of the National Institutes of Health (grant RF1 AG 054442) and the Institute of Advanced Studies of Toulouse and the National Research Agency within the framework of the Investments program. d’Avenir (Investments for the Future) (grant ANR-17-EURE-0010).
More stories on: Aging, anthropology, neurosciences, research