Study spikes notion atherosclerosis is lifestyle disease

Published in The Hindu on March 11, 2013

A study published on Monday (March 11) in The Lancet disproves the notion that atherosclerosis (hardening and narrowing of the arteries) that causes heart attack and stroke is a predominantly lifestyle-related disease and product of industrialisation.

The researchers, who studied 137 mummies from four populations spread across geographically using whole body CT scanning, provide hard evidence that the condition was seen in pre-industrial humans. The populations studied were from ancient Egypt, ancient Peru, the ancestral Puebloans of southwest America and the Unangan of the Aleutian Islands (modern Alaska).

Definite atherosclerosis was seen in 25 mummies and probable atherosclerosis in 22.

This is not the first time atherosclerosis has been seen in mummies. But the study stands out from the previous ones as it is covers more than one population and all strata of society.

In the current study, whole body CT scanning was used to look for signs of atherosclerosis (vascular calcification or build-up of a hard calcified substance along the walls of arteries).

Five arteries were studied — aorta, iliofemoral arteries, tibial arteries, carotids and coronary arteries. Atherosclerosis was predominant (20 per cent) in the aorta, followed by femoral and tibial arteries (18 per cent each), carotid artery (12 per cent) and coronary artery (four per cent).

It found that 34 mummies (25 per cent) had atherosclerosis in one or two arteries, 11 mummies (8 per cent) in three or four arteries, and two (1 per cent) in all five arteries.

The mummies consumed fat-rich food and alcohol. They were also exposed to smoke (from fire used for cooking and for keeping themselves warm), akin to smoking by modern humans, and suffered inflammation due to infectious diseases. Physical activity was “probably prominent” in the populations.

Does that mean the commonly believed risk factors have no bearing whatsoever on atherosclerosis development? “We do not discount any ‘risk’ factors, but rather reinforce the idea that there are multiple interacting environmental, behavioural and genetic factors underlying the atherosclerotic process, both in ancient and in modern humans,” L. Samuel Wann said in an email to this correspondent. “Our knowledge of the risk factors and causative agents for atherosclerosis is incomplete. What we can say about the mummies from these ancient cultures is that they did not consume highly processed foods and probably had little intake of trans-fats.”

Dr. Wann is one of the co-authors of the paper and is from Columbia St. Mary’s Healthcare, Milwaukee, Wisconsin.

But will a completely vegetarian diet help to reduce the possibility of developing atherosclerosis? “While it is unlikely that any of the cultures from which our mummies came embraced a vegetarian diet, a vegetarian or vegan diet does not preclude the development of atherosclerosis in modern humans,” Dr. Wann noted.

“[This] is evidenced by a particularly virulent form of atherosclerosis that affects some modern inhabitants of the Indian subcontinent who have never consumed animal products.”

The chances of developing atherosclerosis increased with age. The severity increased by about 69 per cent per decade of life. This did not change even after adjusting for location (Egypt vs. Americas) and sex. Mean ages for mummies were nearly 37 years for Egyptians and ancient Peruvians; 28 for Ancestral Puebloans and 28.6 for the Unangan.

The authors thus propose that humans do have a more basic “predisposition to the disease.”