South American tribes more resilient to brain ageing than Westerners

The international study, led by Hillard Kaplan of Chapman University, in California, and including researchers from Al-Azhar University, points to ways of improving brain health.

Kaplan and colleagues previously reported that the prevalence of dementia is lower in members of the Tsimane and Moseten populations, who are indigenous to the Amazon forest in Bolivia, than in Westerners² . 

In this latest study, they used computed tomography to measure brain volume in 1,165 Tsimane and Moseten people aged 40-94 years, and assessed its relationship to cognitive function, body mass index (BMI), heart disease, and diet and lifestyle. 

“In the U.S. and Europe, obesity and sedentary lifestyles are associated with faster cognitive decline and smaller brain volumes,” says Kaplan. “When food is abundant and there is little requirement for physical activity, more energy [consumption] leads to worse health outcomes.”  

The Tsimane and Moseten live in non-industrialised societies, leading highly active subsistence lifestyles and having higher exposure to pathogens.  

“Here, we find that a higher BMI is associated with bigger brain volumes for age, except for those at the highest range, who are more like people in wealthy nations,” says Kaplan. “Our take-home message is that there may be sweet spots of food consumption, exercise, and even exposure to pathogens for maximizing health, well-being and cognitive function.” 

Matt Kirkcaldie of the Wicking Dementia Centre, at the University of Tasmania, says the study is “interesting and well conducted,” but should be interpreted cautiously.

“Diet and lifestyle in Western countries are hypothesized to contribute to brain ageing,” he says, “but the loss of brain volume the authors document in the Tsimane and Moseten populations is only slightly less than that seen in U.S. and European populations.”

“It may well be that their aged population has a very different make-up due to differences in lifestyle and high infection rates, making it difficult to identify lifestyle effects.” He adds that although brain shrinkage is observed with age, its relationship to cognition is not entirely clear, so we cannot conclude that 'simpler' lifestyles protect against cognitive decline.

Kaplan's team has funding to follow up the findings. “We plan to conduct a second round of CT scans to measure individual rates of brain volume change longitudinally.” 

“Many Tsimane and Moseten are transitioning towards a more Western lifestyle, so we will investigate the factors associated with individual differences in lifestyle changes and their impacts on diabetes, heart disease, brain volume, and dementia.” 

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