You may recall the data on cardiovascular health published in recent years for the Tsimane population in Bolivia, characterized by a physically active lifestyle and a diet that lacks most of the problem components found in wealthier parts of the world. The rates of cardiovascular disease are far lower in the Tsimane than in US populations. While there are certainly inevitable processes of aging that can only be addressed by the development of new medical biotechnologies, it is also the case that a sizable fraction of cardiovascular and muscle degeneration in the wealthier populations of the world appears to be self-inflicted. Too little physical activity and a diet containing too many calories comes with costs. As the research materials here illustrate, that cost also falls on the brain.
Although people in industrialized nations have access to modern medical care, they are more sedentary and eat a diet high in saturated fats. In contrast, the Tsimane have little or no access to health care but are extremely physically active and consume a high-fiber diet that includes vegetables, fish and lean meat. "The Tsimane have provided us with an amazing natural experiment on the potentially detrimental effects of modern lifestyles on our health."
The researchers enrolled 746 Tsimane adults, ages 40 to 94, in their study. To acquire brain scans, they provided transportation for the participants from their remote villages to Trinidad, Bolivia, the closest town with CT scanning equipment. That journey could last as long as two full days with travel by river and road. The team used the scans to calculate brain volumes and then examined their association with age for Tsimane. Next, they compared these results to those in three industrialized populations in the U.S. and Europe.
The scientists found that the difference in brain volumes between middle age and old age is 70% smaller in Tsimane than in Western populations. This suggests that the Tsimane's brains likely experience far less brain atrophy than Westerners as they age; atrophy is correlated with risk of cognitive impairment, functional decline, and dementia. The researchers note that the Tsimane have high levels of inflammation, which is typically associated with brain atrophy in Westerners. But their study suggests that high inflammation does not have a pronounced effect upon Tsimane brains.
According to the study authors, the Tsimane's low cardiovascular risks may outweigh their infection-driven inflammatory risk, raising new questions about the causes of dementia. One possible reason is that, in Westerners, inflammation is associated with obesity and metabolic causes. In the Tsimane, however, it is driven by respiratory, gastrointestinal, and parasitic infections. Infectious diseases are the most prominent cause of death among the Tsimane.