Mind Mysteries: Sitting Down with Michael Gurven

Illustrated by Bridget Rios

Lauren Luna

Co-News Editor

Michael Gurven and his team studied hunter-gatherer groups in Bolivia for over 15 years. Their research with the Tsimane and Moseten people revealed some information that may uncover unsolved mysteries behind health and aging.

The Tsimane people lead a largely mobile and active lifestyle. As food sources move around or deplete in certain areas, the Tsimane follow it. Their neighbors, the Moseten, are horticulturalists, but also lead non-sedentary lifestyles like their foraging counterparts. Gurven and his team initially studied rates of heart disease among these tribes, finding that they had significantly lower rates of cardiovascular issues than people practicing agricultural, industrialized lifestyles — A.K.A. us.

Chronic diseases often share risk factors, and Gurven’s team questioned if dementia was common among the Tsimane and Moseten. The question carried mixed hypotheses in the beginning, as the two groups lead non-sedentary lifestyles but also carry some risk factors common to dementia, like a lack of schooling. The study, however, proved just the same as those on heart disease among the Tsimane and Moseten.

Alzheimer’s disease, which is a type of dementia, leads as the seventh most common cause of death in the United States. The Center for Disease Control and Prevention estimates that rates of Alzheimer’s will triple by 2060, prompting scientists to learn more about the comorbidities and risk factors associated with the condition. 

Gurven’s study surveyed 435 Tsimane and 169 Moseten elderly members. The study used C.T. brain scanning, cognitive and neurological assessments, and culturally-appropriate questionnaires to look for signs of dementia among the participants. Out of the pool, only five Tsimane individuals showed signs, while only one Moseten individual shared the diagnosis. Alzheimer’s in high-income countries, alternatively, happens to nearly 1 in 10 people over the age of 65. 

“Less than 1 percent [of both populations] had any signs of dementia, and all of them were over the age of 80,” said Gurven to The Bottom Line. “There actually wasn’t anything Alzheimer’s-related among them; most participants showed Parkinsonian-like symptoms when diagnosed.”

A small part of these populations also showed signs of mild cognitive impairment (MCI), which Gurven says can sometimes bridge the gap between normal cognition and dementia-related conditions. Individuals diagnosed with this condition were not included in the results, as MCI does not consistently lead to Alzheimer’s.

According to Gurven, dementia doesn’t exist in the Tsimane language due to its local obscurity. Tsimane people use their native term for “forgetful” to refer to those with the affliction. Symptoms of Alzheimer’s are not understood as a singular condition, but as signs of senility. 

Gurven also emphasized that though the Tsimane and Moseten don’t have a significant share of people with dementia, their genes do not protect them against the disorder. In fact, most Indigenous populations living in industrialized societies have higher rates of dementia than their counterparts, as a culmination of both the industrialized lifestyle and systemic difficulties 

“The details are what matters,” said Gurven. “They’re not running 30 thousand miles a day. They’re actually walking about 17 thousand. Over two-thirds of the calories the Tsimane eat are carbohydrates, but they’re complex carbohydrates.”

Even if we were to try to adopt the Tsimane lifestyle, Gurven said that the possibility does not exist. Though becoming more active and carefully selecting non-processed foods are some methods Gurven suggested, our different environments change how effective these living strategies can be.

Gurven hopes to study more about how the Tsimane and Moseten care for their elderly in future studies, especially those with forms of dementia. Understanding cultural attitudes toward people with such conditions can better inform our own attitudes on elderly care.