What do mummies and atherosclerosis have in common? Lots, it turns out, as Rick and I discuss on this week's PodMed. And while some of this may seem like good news, we hasten to add that just because atherosclerosis is a longstanding condition among humans from all kinds of lineages, that's not carte blanche to consume a bunch of foods of questionable nutritional value and become a couch potato. Okay, so just what exactly did this study reported in the Lancet do?
Whole body CT scans of 137 mummies from four different periods in history, culture and geographic location were obtained. More than 4000 years of human history were represented by this cohort. The mummies hailed from Egypt, Peru, the southwest United States, and the Aleutian Islands. A determination of the presence of atherosclerosis was made based on calcium in the expected course of arteries or a calcified plaque in the wall of an artery.
Atherosclerosis was present in a startling number of the mummies: 38% of the ancient Egyptians, 25% of ancient Peruvians, 40% of the Ancestral Puebloans (US southwest) and 60% of the Aleutian Islanders (Unangan tribe). Wow. That's an overall prevalence of 34%, about as bad as that reported among US servicemen serving in Vietnam, recently reported in another very interesting study of atherosclerosis in JAMA. What is so very impressive about this study is its comprehensiveness: mummies from over 3000 years before Christ, from presumably upper crust Egyptian society were examined alongside those from likely much more modest means from the Aleutian Islands. Everything varied between them, including diet, lifestyle, age at death, and method of mummification. Since this method as well as the overall climate was so very different among the mummies, potential artifacts of preservation potentially accounting for calcification are minimized, and still the condition exists.
The authors point out that previous assumptions about atherogenesis have included sumptuous diet and a lack of vigorous exercise as likely culprits, and that hypothesis was supported by previous work on Egyptian mummies, who only rated mummification if they were of high status, possibly overfed and pampered. This study clearly points to other factors of importance in the laying down of plaque inside arteries. What might they be?
Rick points out that high on this list is chronic inflammation, perhaps due to persistent and recurrent bouts of infectious diseases of all types, and exposure to smoke from indoor fires. Evidence for this last exists in previous studies of lung tissue as well as anthropological investigations of lifestyle among these peoples. Smoke exposure is a particularly attractive hypothesis since the Aleutian Islanders had the highest prevalence of calcification and they were known to be exposed to dense indoor smoke from fires as well as combustion products of whale and seal oil lamps.
What is clear from this study is that we don't fully understand the factors that result in atherogenesis, either among ancient peoples or today. Again, to cite the recent JAMA study that looked at three different populations of US servicemen, we've seen a marked reduction in atherosclerosis over the last 80 years or so, at least among this cohort. Again the smoke hypothesis plays a large role, as many point to the marked decline in cigarette smoking as well as the reduction of saturated fat consumption as factors. This is hopefully a trajectory that will continue, but I am also drawn to the observation that the more we think we know, the more it appears we still need to investigate.
Other topics this week include heart disease after radiotherapy for breast cancer and circulating DNA as a marker for breast cancer metastasis in NEJM, and inappropriate screening colonoscopies in elderly people in JAMA Internal Medicine. Until next week, y'all live well.