PARIS - Scans of mummies from as long ago as 2,000 BC have revealed that ancient people also had clogged arteries, a condition blamed on modern vices like smoking, overeating and inactivity, a study said on Monday.
The finding, published in the Lancet medical journal, casts doubt on our understanding of the condition known as atherosclerosis that causes heart attacks and strokes.
"The presence of atherosclerosis in premodern human beings suggests that the disease is an inherent component of human ageing and not associated with any specific diet or lifestyle," states the study conclusion.
"A common assumption is that the rise in levels of atherosclerosis is predominantly lifestyle-related, and that if modern humans could emulate pre-industrial or even pre-agricultural lifestyles, that atherosclerosis... would be avoided," cardiologist Randall Thompson, one of the authors of the international study, said in a statement issued by Lancet.
"Our findings seem to cast doubt on that assumption, and at the very least, we think they suggest that our understanding of the causes of atherosclerosis is incomplete, and that it might be somehow inherent to the process of human ageing."
This did not mean that lifestyle factors should be discounted, senior author Gregory Thomas, medical director of the MemorialCare Heart and Vascular Institute at Long Beach Memorial Medical Centre in California, told AFP.
They have been shown in study after study to contribute to the development of atherosclerosis, though the degree remains unclear.
"Our study demonstrates... that we are all at risk of atherosclerosis," said Thomas.
"We should do the very best we can to avoid these risk factors. We cannot expect, however, that avoiding them will prevent atherosclerosis."
Atherosclerosis is a hardening and narrowing of the arteries that transport oxygen-rich blood from the heart, through a buildup of fatty material or cholesterol.
The World Health Organisation considers smoking, physical inactivity, a high-salt, high-fat diet and high alcohol use as risk factors.
For this study, the researchers performed full-body computed tomography (CT) scans on 137 mummies from four geographic regions in modern-day Egypt, Peru, southwest America and Alaska.
The mummies were of people who had lived over a 4,000-year period stretching from ancient Egypt in about 2,000 BC to the Unangan hunter-gatherers who lived in the Aleutian Islands of modern-day Alaska as recently as 1930.
The team diagnosed "probable or definite" atherosclerosis in more than a third of the mummies on the basis of calcification of the arteries shown up by the scans.
A similar diagnostic method is used today.
The calcification was found in the same locations as in modern humans, and the appearance was the same.
"Our findings greatly increase the number of ancient people known to have atherosclerosis and show for the first time that the disease was common in several ancient cultures with varying lifestyles, diets and genetics, across a wide geographical distance and over a very long span of human history," the scientists wrote.
"These findings suggest that our understanding of the causative factors of atherosclerosis is incomplete."
The mummies of older people were more likely to show signs of the disease, just as in humans today.
Other research cited in the study has found atherosclerosis to be common in people living today, even ubiquitous in men by age 60 and women by 70.
"We simply don't know enough about the diet and lifestyle of the people studied to say whether behaviour or genetics lies at the root" of the disease, the British Heart Foundation said in a comment on the study.
And Grethe Tell, an expert with the European Society of Cardiology, told AFP the findings "do not refute" that an unhealthy lifestyle increased the risk of heart attack and stroke.
"Not everybody who has atherosclerosis (whatever the cause may be) gets clinical disease," she explained.
"Lifestyle factors increase the risk of heart attacks and may therefore be a triggering factor in the chain between atherosclerosis and heart attack."
According to the study, the ancient populations' diets had been varied -- including everything from shellfish and fish, game, domesticated cattle, sheep, pigs and ducks to a wide variety of berries, farmed maize, beans and potato -- even beer and wine in the case of the Egyptians.
None of the groups were known to be vegetarian, and physical activity was probably high.
Smoke inhalation may have played a role, as many of the communities used indoor fires for cooking and heating.
Clogged arteries previously observed in ancient Egyptian mummies had hitherto been attributed to a high-fat diet of the elite -- as poor people in those communities were not mummified.
The latest findings also refute that conclusion.