Six Hours Per Day

An article from the Duke University media outlet reminds us of the bigger historical picture of human life expectancy: continual incremental improvement ever since the Industrial Revolution. It's also a good example of how to write a decent popular science press piece, one that adds context to the research it references, rather than dumbing it down or papering it over. From the perspective of the reliability theory of aging and longevity, the historical increase in life expectancy has occurred because better and more widespread availability of medical technology lowers the rate at which biological damage accumulates. Prevention of chronic infectious disease, for example, falls into this category: disease applies a damage load to an individual, and that damage reduces the mean time to failure of bodily systems.

"We're living longer because people are reaching old age in better health," said demographer James Vaupel, author of a review article appearing in the March 25 edition of Nature. But once it starts, the process of aging itself - including dementia and heart disease - is still happening at pretty much the same rate. "Deterioration, instead of being stretched out, is being postponed." ... Over the past 170 years, in the countries with the highest life expectancies, the average life span has grown at a rate of 2.5 years per decade, or about 6 hours per day.

Six hours per day sounds a lot more exciting than a few years per decade - there's a lesson about the time preference of human psychology lurking in there somewhere. Advocates take note: tell your friends how many extra hours of life they gained today thanks to advancing medical technology, and see what they say.

But to return to the article, the other lesson here is that changing longevity changes human society - entirely for the better so far. The effect is somewhat delayed in modern times, as people look to their parents for the course of their own life - which is not going to help much in today's world of accelerating biotechnology. We will have access to technologies of engineered longevity that weren't even science fiction twenty years ago. But people are structuring their lives differently to those of their grandparents precisely because they expect to live noticeably longer:

It also may be time to rethink how we structure our lives, Vaupel said. "If young people realize they might live past 100 and be in good shape to 90 or 95, it might make more sense to mix education, work and child-rearing across more years of life instead of devoting the first two decades exclusively to education, the next three or four decades to career and parenting, and the last four solely to leisure."

One way to change life trajectories would be to allow younger people to work fewer hours, in exchange for staying in the workforce to a later age. "The 20th century was a century of the redistribution of wealth; the 21st century will probably be a century of the redistribution of work," Vaupel said.

I've looked at this topic numerous times in the past; you might dig back into the archives and take a look at these posts, for example:

One last note: that we can talk about "allowing" people to work in the context of what government bureaucrats in many regions write into law and enforce by threat of jail - mandatory retirement, for example - is a great iniquity. It is vile that one group of privileged people force their way into the private contracts of others:

Retirement forced on people who are perfectly capable and willing to work is a terrible thing. Only in a dreadfully twisted social environment can more willing workers be transformed from boon into problem. Sadly, most of us live in just such a society, repleat with forced wealth transfers, counterproductive medical regulations, and the tragedy of the commons writ large upon taxed wealth and shoddy government monopoly services. This is what happens when socialist ideas prosper.

ResearchBlogging.orgVaupel, J. (2010). Biodemography of human ageing Nature, 464 (7288), 536-542 DOI: 10.1038/nature08984