New Delhi, March 11: Scientists have discovered evidence of blocked arteries in ancient humans with diverse diets, lifestyles and genetic backgrounds in a study that questions the assumption that atherosclerosis is primarily an affliction of modern times.
Atherosclerosis is a hardening and thickening of arteries as fatty materials such as cholesterol build up in their walls forming hard structures called plaques. Over time, these plaques can block the arteries, making the disease a leading cause of heart attacks and strokes.
The researchers used computerised tomography (CT) scans to examine 137 mummies — intentionally embalmed or naturally preserved human bodies — from periods up to 3100 BC from four distinct geographical locations. They found atherosclerosis in 47 bodies.
Their findings, published yesterday in The Lancet, a medical journal, suggest that atherosclerosis was common in pre-industrial and even pre-agricultural populations of hunter-gatherers.
The study probed 76 mummies from Egypt, 51 from Peru, five from the ancient Puebloan tribe in southwest US and five from the Aleutian Islands near Alaska. The bodies span 5,000 years of human history, from the Egyptian mummies of 3100 BC to the 19th-century Aleutian islanders.
The four populations had diverse diets. The Egyptians ate wheat, dates, figs and the meat of domesticated cattle, sheep and goats; the Peruvians grew corn, potatoes and bananas and hunted deer and birds; the Puebloans ate maize, amaranth and pine nuts and hunted rabbit and mule deer; and the Aleutian islanders were hunter-gatherers, catching fish, seals and otters.
But the scientists found atherosclerosis in each population: 29 Egyptian and 13 Peruvian mummies and two of the five Puebloans and three of the five Aleutian islanders had signs of the disease in one or more of their arteries.
“We need to rethink the relative importance of (the traditionally acknowledged) risk factors for atherosclerosis,” Randall Thompson, a cardiovascular medicine specialist at the University of Missouri-Kansas City School of Medicine in the US and the lead author of the study, told The Telegraph.
Over the past several decades, health researchers have assumed that atherosclerosis is primarily associated with certain aspects of modern life such as high blood pressure, health-unfriendly diets, lack of exercise and smoking.
Some have even speculated that emulating the food and living habits of pre-industrial or hunter-gatherer populations might help curb the growth of atherosclerosis observed over the past 200 years.
“But our findings suggest that we don’t understand the risk factors as well as we think we do,” Thompson said in a telephone interview. “Atherosclerosis seems to be the result of a complex interaction of genetics, environment and ageing.”
Studies in the past have revealed atherosclerosis in Egyptian mummies. In 2009, Thompson and his colleagues had shown that 20 of a set of 44 Egyptian mummies had blocked arteries.
But the significance of those findings remained unclear because some scientists argued that the ancient Egyptians embalmed the bodies of individuals with high socio-economic status in their society, who may have had lifestyles similar to modern-day populations.
The new study, with its findings of blocked arteries in three new populations, bolsters the case for ancient atherosclerosis. The CT scans have suggested that the older the individual was, the greater was the severity of the atherosclerosis in arteries carrying blood to the heart, brain and the legs.
But doctors caution that the findings should not in any way undermine the importance of regulating diet and lifestyle to reduce the risk of atherosclerosis.
“The key message for us living in modern times is that low risk should not be treated as zero risk,” Jagat Narula, an Indian-born cardiologist and member of the study team at the Mount Sinai Medical Centre, New York, told this newspaper.
The “paleocardiologists”, as Narula and Thompson sometimes call themselves, also caution that some lifestyles are obviously healthier than others.
“If there are some things we cannot control, that’s all the more reason to control things like diet and lifestyle,” Thompson said.
“We can’t turn away from our traditional risk factors,” said Narula, who was a fellow in cardiology at the All India Institute of Medical Sciences, New Delhi, in the late 1980s before leaving for the US.
The mummies from Peru, southwest US, and the Aleutian Islands were naturally preserved under local climate conditions.
“It’s reasonable to assume these mummies represent a cross-section of the population, rather than (an) elite group of people selected (specially) for mummification (as) in Egypt,” Thompson said in a media release issued by the journal.
The study’s findings were presented last evening at a conference of the American College of Cardiology in the US.