"You're only as old as you feel", or so the saying goes.
Many people would like to be a little bit sharper, with our cognitive function naturally declining with age. An indigenous group in the Amazon may be the exception, however.
Scientists from the University of Southern California (USC) have reported how Bolivia's Tsimane people maintain more of their brain volume into old age, with these cells being lost among their American and European counterparts.
Reduced brain volume has been linked to cognitive decline and even dementia.
While the Tsimane have little or no access to modern healthcare, the scientists have described them as being "extremely physically active" – farming, fishing and hunting to bring home vegetables, fish and low-fat meat.
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The Tsimane people first hit the headlines in 2017 for having the lowest prevalence of coronary atherosclerosis – a build-up of plaque in the arteries that supply blood to the heart – of any known population.
"The Tsimane have provided us with an amazing natural experiment on the potentially detrimental effects of modern lifestyles on our health," said study author Dr Andrei Irimia.
"These findings suggest brain atrophy may be slowed substantially by the same lifestyle factors associated with very low risk of heart disease."
Brain atrophy describes a loss of nerve cells, and the connections between them, in the vital organ.
It is increasingly coming to light that what is good for the heart is good for the mind, with a healthy lifestyle benefitting both the cardiovascular system and the brain.
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The USC scientists analysed 746 Tsimane adults, aged 40 to 94, of the approximately 16,000-strong group.
The adults spent up to two days travelling – by river and road – from their remote villages to Trinidad, the closest town with CT scans.
Results – published in the Journal of Gerontology, Series A: Biological Sciences and Medical Sciences – reveal the difference in brain volume between the middle-aged and elderly Tsimane people was 70% smaller than among their counterparts living in three "industrialised populations" in the US and Europe.
The Tsimane people had higher levels of inflammation, however, which has been associated with brain atrophy, along with other diseases.
Nevertheless, this inflammation was not found to have a "pronounced effect" on the Tsimane people's brains.
In developed countries, inflammation is often linked to obesity, high blood pressure, elevated cholesterol and fat around the waist.
Among Tsimane people, infections may trigger inflammation, with parasites being the leading cause of death among the indigenous group.
"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," said co-author Professor Hillard Kaplan, from Chapman University in California, who has studied the Tsimane for nearly 20 years.
"This study demonstrates the Tsimane stand out not only in terms of heart health, but brain health as well.
"The Tsimane can serve as a baseline for healthy brain ageing.
"The findings suggest ample opportunities for interventions to improve brain health, even in populations with high levels of inflammation."
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