By
Jim Wood
A
recurrent theme of this bog has been about how best to invest the limited
resources available for biomedical research.
I have a peculiar (but I think useful) perspective on this question that
grows out of my professional interest in long-term population history.
I
study the population dynamics of preindustrial societies. Some of my work involves historical
demography, some of it involves working with traditional farming communities in
remote parts of the developing world, all of it involves asking questions about
the relationship between the ecology of food production and
health/morbidity/mortality, especially among the very young. So my view of the contemporary scene in the
U.S. tends to be that of someone peering out from the Neolithic or some other
long-dead period of the past. And from
that point of view, my take on the modern health care crisis in the developed
world is: “Crisis?! We should only have such crises!” Let me
explain.
Since
the eighteenth century, average human life span (or rather life expectancy at
birth, which is not necessarily the same thing) in the Western World has
roughly doubled – that is, it’s increased by about 40 years. How can we now achieve a comparable, further increase in U.S. life span based
on the kinds of new medical research that are currently being touted? My answer:
We can’t. And we probably
shouldn’t even try.
The
dramatic increase in life expectancy in European and European-derived
populations during the nineteenth and the first half of the twentieth centuries
had to do almost exclusively with a decrease in early childhood mortality. It had very little to do with health and
survival among the elderly or what we would now (fashionably) call “life span
extension”. In addition, the historical
decline in mortality was attributable entirely to changes in environmental conditions, especially
exposure to infectious diseases and the ability to fight off such diseases,
reflecting (among other things) the immunological effects of under-nutrition
and thus the sufficiency and reliability of the food supply. (In America today we may have lousy diets from
many points of view, but nobody can claim that most of us ever go hungry.) Past medical advances had surprisingly limited
effects on this dramatic drop in mortality at the aggregate (population) level. The “wonder drugs” of my youth – penicillin,
streptomycin, etc. – certainly saved lives, but most of the historical decline
in mortality had already occurred by the time those antibiotics and most
vaccines came onto the scene. (Note: I
am not disparaging vaccines, which I think are a blessing.) Thanks in part to the evolution of
drug-resistant strains of pathogens, infectious diseases are making a bit of a
comeback these days, but they are very far indeed from dominating human mortality
patterns the way they once did – except, of course, in parts of the present-day
developing world.
Since
the 1950s, there have certainly been improvements in life expectancy in the
West, mostly having to do with the ongoing campaign against smoking and, probably, with a
better understanding of the role of dietary factors in cardiovascular disease
(again, environmental exposures). But
the improvements have been small, and they have been getting smaller and
smaller – despite the ever-spiraling costs of medical research and health care.
But
now we are entering (supposedly) a Brave New World of genomic medicine and life
span extension – a Brave and Unbelievably Expensive
New World in terms of both research dollars and medical care costs. This investment will, we are reliably
informed, lead to our living active, healthy lives until age 120 or older. In the future, 120-year olds will be hard to
distinguish from present-day 45-year olds.
And much of this advance will come from research on the genetics of life
span.
As
is frequently pointed out on this blog, there are a few major genetic
diseases having substantial effects on mortality, and these diseases have long
been known and have mostly already been mapped, at least approximately, using
what would now be regarded as pretty old-fashioned, low-tech methods. While treating these diseases can certainly
improve individual health and
survival, they are mostly so rare that even the most effective treatments would
have little effect at the demographic level.
And, because they’re so rare, there’s little economic incentive to
invest in their further study. There’s
something else worth noting about these major genetic diseases: they mostly
kill at comparatively young ages, so even their total elimination would have
basically zero effect on the overall human life span.
Beyond
that, genomic medicine has, as Anne Buchanan and Ken Weiss regularly point out here on MT, contributed pretty much nothing to aggregate human
health and is unlikely to do so in the future.
I would say the same is true of gerontological science (hang on to those
telomeres, kids!). Recent increases in
life expectancy at birth, while real, have been nugatory compared to the
historical shift in rates and causes of death.
The idea that we can achieve another 40-year increase in life expectancy
is delusional.
Interestingly,
a new Pew Charitable Trust poll shows that most Americans are not particularly
attracted by the idea of living to 120, even if they are assured of being
active, healthy, and alert at that age.
As it happens, I am only one degree of separation from the world’s only
well-documented case of human survival past age 120 – Jeanne Louise Calment,
who died in southern France about fifteen years ago aged 122. My colleague Jim Vaupel, who was part of the
team of demographers who verified the paper trail linking Madame Calment to her
birth records, was invited to her 120th birthday party. Afterwards I asked how she was. His reply: “REALLY OLD!!!” She sure as hell didn’t look 45. She was blind and deaf, slipping into dementia,
and in general extremely decrepit. As is
the case of most of the oldest old today, her extraordinary longevity had
doomed her to years of physical disability and severely impaired functionality. For my part, I’ll pass on such a medical
miracle.
From
my Neolithic point of view, only a few pieces of health advice have ever made
much difference at the population level: eat as much food as you can (as
Michael Pollan would add, mostly plant material), avoid famines and plagues,
don’t smoke tobacco (or at least don’t inhale), and keep your latrines as far
away from your sources of drinking water as you reasonably can. Oh yeah, and think about maybe using mosquito
nets if they’re available. “Don’t live
in swamps” is also pretty good advice.
Everything else is hype.
My
overall conclusion is that the only truly important – and potentially solvable
– health problems in the world today are found overwhelmingly in developing
countries. Genomics and gerontology are
not going to help solve those problems.
Mind you, the right kind of
medical research can certainly contribute toward finding solutions, but only if
it can attract funding in today’s market.
And much good work can be done on the cheap. Think of what would happen if we diverted the
money currently invested in, say, genome-wide association studies and used it
to buy mosquito nets or oral rehydration packs for the tropics. Why, then, are we investing all our resources
in the kinds of “modern” ailments that only affect the well-off and already
long-lived? As my Neolithic (or Third
World) farmer would say, “Crisis?! We
should only have such crises!”
