Members of an indigenous Amazonian group known as the Tsimane experience significantly less brain atrophy than Americans and Europeans as they age, according to new research. The study authors believe that the active lifestyle and high-fiber diet of the Tsimane are the primary causes of this reduction in cerebral deterioration and that adopting elements of their way of life could help prevent age-related cognitive decline and dementia.
The Tsimane are well known for their cardiovascular health, with a 2017 study indicating that 85 percent have no calcium build-up in their arteries, meaning their risk of heart disease is virtually zero. This held true for around two-thirds of those over the age of 75, leading scientists to hail the group’s hearts as the healthiest ever observed.
Consisting of around 17,000 individuals, the Tsimane inhabit an isolated area of the Bolivian Amazon and have little or no access to modern medicine or healthcare. The group primarily engages in activities such as hunting, gathering, fishing, and farming, while consuming a diet that is rich in vegetables and lean meat. In contrast, Western populations typically live more sedentary lives and consume a diet that is high in sugar, fat, and processed foods.
To analyze the effect this has on brain health, the study authors invited members of the Tsimane to undertake a two-day journey to the nearest laboratory with computed tomography (CT) scanning equipment. A total of 746 individuals, ranging from 40 to 94 years old, took up the offer.
Reporting their findings in The Journal of Gerontology, Series A: Biological Sciences and Medical Sciences, the researchers describe how they calculated the volume of each participant’s brain, and used this data to examine the rate at which the Tsimane’s brains shrink as they age. They then compared this to existing data regarding age-related reductions in brain volume among three cohorts in Germany, the Netherlands and the US.
A comparison of the various cohorts revealed that Tsimane brains age 70 percent slower than their Western counterparts, as evidenced by smaller differences in brain volume between middle age and old age. This is highly significant, as brain volume loss is associated with dementia.
"These findings suggest that brain atrophy may be slowed substantially by the same lifestyle factors associated with very low risk of heart disease,” explained study author Andrei Irimia in a statement.
Interestingly, however, the researchers note that the Tsimane are known to have high rates of inflammation. This is somewhat puzzling, as inflammation is known to play a role in brain aging in Westerners, yet somehow appears not to affect the brains of older members of the Amazonian group.
By way of explanation, the study authors propose that the inflammation seen in the Tsimane is of a different kind to that experienced by Westerners, as it is primarily triggered by infections rather than by metabolic causes or obesity. This implies that it is not inflammation per se that causes brain atrophy, but the unhealthy lifestyles that generate this inflammation in certain populations.
Summing up these conclusions, study author Hillard Kaplan explained 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."