Life expectancy: what really mattered

National Geographic has a great series up on global population growth. We'll hit 7 billion people in 2011 - quite a milestone. One thing to quibble about from the article:

Moreover in 1798, the same year that Malthus published his dyspeptic tract, his compatriot Edward Jenner described a vaccine for smallpox—the first and most important in a series of vaccines and antibiotics that, along with better nutrition and sanitation, would double life expectancy in the industrializing countries, from 35 years to 77 today. It would take a cranky person to see that trend as gloomy: “The development of medical science was the straw that broke the camel’s back,” wrote Stanford population biologist Paul Ehrlich in 1968.

I've read statements like this - about increasing life expectancy and its reasons - many times, and it's almost always done in a certain order. Here, life expectancy increases result from "a series of vaccines and antibiotics that, along with better nutrition and sanitation..." It's hardly the most egregious wording I've seen. Often I'll read that "modern medicine" led to increases in life expectancy, so it's nice that the article specifically mentions vaccines, a preventive measure, instead of only the curative parts of modern Western medicine that we're more familiar with as adults.

But the even the formulation "vaccines and antibiotics along with better nutrition and sanitation" still seems problematic. Why is nutrition and sanitation always an afterthought? I don't have a citation handy, but my impression is that the vast majority of the increase in life expectancy stemmed from advances in sanitation and nutrition, while curative medicine (including antibiotics) played a much more minor role. (I would love to read a good paper outlining the relative contribution of changes in nutrition, sanitation, vaccination, antibiotics to life expectancy improvements - if you know of one, please post it in the comments.)

I think this bias stems in part from a larger bias toward seeing advances in public health as medical advances, rather than societal, economic, or political ones. Many (too many?) people working in the public health field have medical backgrounds. Modern medicine is shiny and fancy and dramatic, and (credit where it's due) has made some incredible advances.

Imagine you're given a Rawlsian choice between being born into:

  • World A, with the nutrition, sanitation and vaccination of modern Europe but with all of the doctors and drugs mysteriously raptured in a giant Hippocratic tribulation, or
  • World B, with the nutrition, sanitation and vaccination of ancient Rome but with Atul Gawande on standby with the latest treatments once you get sick

I'd definitely choose World A. (Though I'm glad we don't have to choose!)

To correct this bias, I think it would helpful if every time we mentioned the dramatic shift in life expectancy over the past few centuries, we emphasized that most of those gains are from reductions in child mortality, and that nutrition and sanitation deserve the lion's share of credit for those improvements. At the least, let's mention them first and then say "along with later, less important developments such as antibiotics."