In a 1971 paper that profoundly influenced how scientists and policy makers approached public health issues Abdel Omran set out his theory of "The Epidemiologic Transition". He hypothesized that societies went through three different ages, or phases, that defined their experience with regard to mortality and life expectancy. In the first, the "age of pestilence and famine", life expectancy is low and episodes of widespread death are common. In the second, the "age of receding pandemics", infectious diseases are overcome and life expectancy increases dramatically. Finally, in the third, the "age of degenerative and man-made diseases", diseases of aging and self-inflicted suffering becomes the predominant determinant of mortality. Eventually others, noting the dramatic increase in life expectancy due to the rapid decline in deaths due to heart attack and stroke, posited a fourth age; essentially the same as the original third age but with cardiovascular disease removed from the "degenerative disease" category.
Now in an editorial in this month’s JAMA Dr. Michael Gaziano asserts that we may be entering a fifth phase, or age, of the epidemiologic transition. We are now, he writes, entering the "age of obesity and inactivity" in which ailments due to gluttony and sloth predominate on death certificates. The editorial references two new articles in the same issue purporting to show Americans are fat and getting fatter; especially the children.
But wait a minute. The age of man-made diseases barely materialized. Certainly there have been many many cases of people suffering terribly as a result of some man-made health hazard. Look no further than the cases of mesothelioma among the men who served aboard amosite laden Navy ships. And smoking continues to exact its terrible toll. Yet if you throw all the deaths due to occupational diseases and every last lung cancer/COPD death into the same category you can’t get to 10% using worst case estimates. More sober estimates put the percentage of deaths due to man-made diseases at considerably less than one. Nevertheless, this powerful meme - that most of our woes are self-inflicted and due to some failure to live in a natural way – still propels not only mass tort litigation but also much scientific and political thinking.
However, there’s more than just AIDS to demonstrate that we never really saw the "disappearance" of infectious diseases. Go to www.pubmed.gov/ and do some searches on helicobacter pylori and humanpapilloma virus and you’ll see just how many cancers are now being attributed to just these two organisms. Investigate mollicutes and you’ll find that all sorts of microbes are suddenly being found associated with disease and they’re only now being found because the technology to identify them is only now being refined.
Finally, remember to read the fascinating journey of Barry Marshall and Robin Warren from authors of an abstract rejected as one of the year’s worst to winners of the Nobel Prize in Medicine for the very same work. In the end, the view, supported by the work of one of the world’s preeminent public health researchers, that peptic ulcers were caused by that most modern of man-made insults, stress, only gave way to the understanding that the cause was in fact a bacteria when the evidence was irrefutable.