Heart disease is the leading cause of death in the United States, according to the Center of Disease Control, but a research team has found a group of people unfazed by harms of one common heart issue.
The research team, which included ASU assistant professor Ben Trumble, found that the hearts of the Tsimane, an indigenous Amazonian tribe that live in the lowlands of Bolivia, were not affected by coronary artery disease as much as those in the United States.
The researchers focused the presence of coronary atherosclerosis, commonly known as coronary artery disease, in the Tsimane in order to determine and subsequently compare heart health.
“Atherosclerosis involves progressive buildup of lipids and plaque in the arteries that, depending where, there can be a plaque rupture or event that leads to a clot and obstructs blood flow," said Michael Gurven, a professor of anthropology at the University of California Santa Barbara and codirector of the Tsimane Health and Life History Project. "If blood flow is obstructed to the heart you can have a heart attack, and if blood flow is obstructed to the brain you can have a stroke."
He said levels of atherosclerosis were measured through a Coronary Artery Calcium Scan (CAC), chosen because of its noninvasive nature and effectiveness.
“Not all plaques have calcium, but it is considered the best non invasive technique for estimating the degree of atherosclerosis,” said Hillard Kaplan, a professor of anthropology at the University of New Mexico and co-director of the Tsimane Health and Life History Project.
A CAC test involves a taking a computerized tomogram (CT) scan of the chest, he said. The CAC test is able to measure the amount of calcium that has accumulated along the coronary arteries in the body.
According to the study, results from the CAC test are scored on a scale where a score of zero indicates that there was no identifiable plaque and a score of 100 and above indicates that a moderate amount of athersclerotic plaque is present in the coronary arteries, Trumble said.
“So if you have a coronary artery calcium score of zero that means you have no atherosclerosis and approximately 85 percent of people in this sample have no atherosclerosis," Trumble said. "In comparison, 85 percent of people in the US in the same age range have some atherosclerosis.”
Despite low levels of coronary atherosclerosis, the Tsimane population sampled had high levels of inflammation, he said.
“In the U.S., and other population samples in Europe, individuals with higher levels of inflammation are at much higher risk of heart disease," Trumble said. "In fact inflammation is involved in every single process from plaque formation to plaque rupture and then the clots forming and the person having a heart attack. So inflammation is involved in every aspect of heart disease.”
The factors causing inflammation in the Tsimane people, however, differ from the factors that lead to inflammation in the United States, he said. High inflammation in individuals in the United States is usually attributed to factors like smoking or obesity, none of which are responsible for inflammation in the Tsimane people.
“Inflammation that the Tsimane are experiencing is coming from things like a high parasite load and high pathogen load," Trumble said. "More than two-thirds of Tsimane have intestinal parasites at any given time."
He said the Tsimane people have the lowest levels of coronary atherosclerosis ever studied. Researchers in the study cite that possible explanations for this are coronary artery disease risk factors, subsistence lifestyles, genetics and inflammation or immune regulation.
“We can’t say whether it’s diet, or physical activity, or immune activation," Trumble said. "We know that all three are important. We are doing studies now to try and differentiate out what are the most important factors but overall we don’t think there is going to be a silver bullet ... it’s going to be a combination of these factors that result in the Tsimane having the healthiest hearts ever seen."
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