You may be referring to information stemming from a study of natives in the Bolivian Amazon, the Tsimane, who reportedly experience less brain atrophy with age than Americans and Europeans. The Tsimane are believed to have the world’s healthiest arteries, and their brains are said to age 70 percent more slowly than ours do.
A study published in 2017 found that these people also have extraordinarily healthy hearts in older age and the lowest prevalence of coronary atherosclerosis of any known population.
Researchers believe that the health of the Tsimane is likely related to their pre-industrial subsistence lifestyle. They eat vegetables, fish, and some lean meat and are extremely physically active as hunters, fishers, and foragers.
After studying the Tsmaine more recently, researcher Andrei Irimia, Ph.D., of the University of Southern California concluded that these natives “have provided us with an amazing natural experiment on the potentially detrimental effects of modern lifestyle on our health.” In a study published this year (2021), he added that the latest findings suggest that brain atrophy may be slowed substantially by adopting the same lifestyle practices associated with a very low risk of heart disease.
The USC researchers used brain scans conducted in the closest town to the Tsimanes homeland where CT scanning equipment was available. The scans enabled the researchers to determine that shrinkage in Tsimane brain volume between middle age and old age is 70 percent less than it is among Western populations. Brain atrophy is correlated with cognitive impairment, functional decline and dementia.
According to study author Hillard Kaplan, Ph.D., a professor of health economics and anthropology at Chapman University who has studied the Tsimane for nearly two decades, “The Tsimane can serve as a baseline for healthy brain aging.” He added that “our sedentary lifestyle and diet rich in sugars and fats may be accelerating the loss of brain tissue with age and making us more vulnerable to diseases such as Alzheimer’s.”
Andrew Weil, M.D.
Andrei Irimia and Hillard Kaplan et al “The indigenous South American Tsimane exhibit relatively modest decrease in brain volume with age despite high systemic inflammation.” The Journals of Gerontology: May 26, 2021, DOI: 10.1093/gerona/glab138