Rates of dementia among an indigenous Amazonian tribe are 11 times lower than in the West, researchers have found.
The study of the remote Tsimane community builds on previous research which found that the same groups display almost no cases of heart disease.
Researchers at the University of California believe the 16,000-strong group’s ‘pre-industrial subsistence lifestyle’ could explain the low incidence of dementia.
Scientists analysed dementia rates among over-60s in the Tsimane community and neighbouring Moseten tribe.
The team looked for signs of dementia using CT scans and neurological tests.
The tribe members were also asked to complete questionnaires to reveal to what extent cognitive impairment was impacting on their lives.
Just five out of 435 Tsimane people and one of the 169 Moseten group had dementia, about 1 per cent over all.
Meanwhile, dementia rates in the UK are around 7 per cent and 11 per cent in the US.
Lead author Professor Margaret Gatz, an ageing and preventative medicine expert at USC, said:
‘Something about the pre-industrial subsistence lifestyle appears to protect older Tsimane and Moseten from dementia.’
Up to 10 per cent of people in the communities had some mild cognitive impairment (MCI), including memory, language and spatial awareness loss.
The researchers could not explain why MCI rates were normal while dementia rates were so low.
However, those with either condition were more likely to have calcium deposits in the arteries supplying blood to the brain.
Calcification can be linked to high cholesterol diets common in the West.
The Tsimane diet, meanwhile, consists mostly of high-fibre carbs, including rice, corn, nuts and fruits.
The community eat an average of just 38g of fat a day, 11g of saturated fat and no trans fats.
Professor Hillard Kaplan, who led the study, said:
“We’re in a race for solutions to the growing prevalence of Alzheimer’s disease and related dementias.
“Looking at these diverse populations augments and accelerates our understanding of these diseases and generate new insights.”
Co-author Professor Benjamin Trumble, an evolutionary biologist at Arizona State University, added:
“By working with populations like the Tsimane, we can get a better understanding of what human health was like in different environments before industrialisation.
“What we do know is the sedentary, urban, industrial life is quite novel when compared with how our ancestors lived for more than 99 per cent of humanity’s existence.”