It is well known that life expectancies increased significantly during the 20th century in the U.S. While this was certainly a positive development, highly aggregated statistics such as life expectancy can mask problems that become apparent when you look beneath the surface. In particular, the marked decline in mortality from infectious diseases greatly boosted life expectancies, and more than offset the impact of the gradual but large increase in the incidence of various deadly conditions (cardiovascular disease, cancer, diabetes, suicide). These latter conditions are sometimes referred to as “diseases of civilization”.
To understand why this would be the case, consider an illustrative example. Infectious diseases took a greater toll on younger people. A person who might have died at, say 10 years old, but instead survived and lived to say, 75 years old, contributes an extra 65 years of life to the overall life expectancy calculation. Now consider someone who is a victim of the increase in cardiovascular mortality and dies from a heart attack at age 65. He may otherwise have only lived to age 75, so this extra death only reduces his contribution to life expectancy by 10 years. If there were equal numbers of people saved from infectious disease and killed by cardiovascular disease, each affected pair would add 55 years to the life expectancy calculation for the population.
Up until recently, there was not a satisfactory explanation for the rise in the diseases of civilization. The prevailing wisdom is that these diseases are due to changes in diet, sedentary lifestyle, increased crowding in cities, cigarette and alcohol consumption, and disintegration of societal and family support. While these explanations sound plausible,…