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Dean Pomerleau

Are Increases in Life Expectancy Leveling Off or Marching Higher?

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Al Pater posted this review article [1] from way back in 2002 on the question of whether or not worldwide life expectancy is really beginning to level off, or is marching higher at the same 1/4 of a year per year rate that it has for the last 150 years. Here are two graphs from the paper, the first showing how striking and consistent the trend towards a higher lifespan has been, and how virtually everyone predicts it is going to level off (dashed red lines at the top):

 

SPjKalh.png

 

The authors postulate that the impression people have that lifespan is constantly on the verge of plateauing is an illusion with a few different causes. One interesting one is political. Politicians tend to low-ball when it comes to estimating future gains in life expectancy to make the cost of social programs, particularly those directly at the elderly like social security, medicare, look less costly and burdensome on the future. More interestingly, and with more evidence it would seem, they suggest the apparent leveling off in life expectancy gains is a result of the fact that the leading nation in life expectancy improvements keeps changing, with some countries (like the US) falling off the cutting edge, while other countries, like Japan, pick up the torch and push life expectancy higher at the same old rate of 1/4 of a year per year. So for the citizen in most countries, they fact is that lie expectancy improvements have levelled off. They give as evidence for this effect this graph:

 

gcXG4C7.png

 

As you can see, Japan comes up after WWII to overtake the rest of the world in life expectancy, and keep us on the linear curve of life expectancy increases. Here are the authors' three rather bold assertions in the concluding paragraph of the paper:

 

This mortality research has exposed the empirical misconceptions and specious theories that underlie the pernicious belief that the expectation of life cannot rise much further. Nonetheless, faith in proximate longevity limits endures, sustained by ex cathedra pronouncement and mutual citation (1, 8, 9). In this article we add three further lines of cogent evidence. First, experts have repeatedly asserted that life expectancy is approaching a ceiling: these experts have repeatedly been proven wrong. Second, the apparent leveling off of life expectancy in various countries is an artifact of laggards catching up and leaders falling behind. Third, if life expectancy were close to a maximum, then the increase in the record expectation of life should be slowing. It is not. For 160 years, best-performance life expectancy has steadily increased by a quarter of a year per year, an extraordinary constancy of human achievement.

 

As I said - bold words.

 

So that was in 2002. It's been almost a decade and a half since the paper was written. Have gains in life expectancy continued their "steadily increased by a quarter of a year per year" that the authors observe happening for the last 160 years?

 

Nope - Not quite at least. Japan remains #1, and here is a graph of Japanese life expectancy that includes the period between 2002 through 2014:

 

n-longlife-a-20150801.jpg

 

The paper reports in 2002 the life expectancy of a Japanese female was "almost 85 years", and in 2014 it was almost 87 years. So that is a life expectancy increase of 2 years in 12 years, or one sixth of a year per year, rather than the quarter of a year per year trend the authors point to. That equates to an average yearly shortfall in lifespan gains of 33% relative to the authors' prediction. Of course, this may be just a short-term deviation away from the long-term trend. Perhaps new advances in treatments or therapies for the diseases of aging (e.g. stem cell therapy, CRISPR-based gene therapy) will come along and keep us on the curve. 

 

It reminds me of the supposedly inexorable Moore's Law that futurist and immortality-optimist Ray Kurzweil likes to point to, namely that computer power (actually transistor count) doubles every two years, like clockwork, and has been for at least the last 40-50 years, and much longer than that if you ask Kurzweil. Unfortunately, I looks like we're falling off that curve too, according to this recent article in Nature (Feb '16):

 

Next month, the worldwide semiconductor industry will formally acknowledge what has become increasingly obvious to everyone involved: Moore's law, the principle that has powered the information-technology revolution since the 1960s, is nearing its end.

 

Similarly, at this point we seem to be slowing down rather than speeding up increases in life expectancy which would move us toward longevity escape velocity, where life expectancy increases by (at least) one year per year.

 

--Dean

 

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[1] Science. 2002 May 10;296(5570):1029-31. No abstract available.

 

Demography. Broken limits to life expectancy.

 
Oeppen J, Vaupel JW.
 
 
Summary
 
Is human life expectancy approaching its limit? Many--including individuals
planning their retirement and officials responsible for health and social
policy--believe it is, but the evidence presented in the Policy Forum
suggests otherwise. For 160 years, best-performance life expectancy has
steadily increased by a quarter of a year per year, an extraordinary
constancy of human achievement. Mortality experts have repeatedly asserted
that life expectancy is close to an ultimate ceiling; these experts have
repeatedly been proven wrong. The apparent leveling off of life expectancy
in various countries is an artifact of laggards catching up and leaders
falling behind.
 
PMID: 12004104
 

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Similarly, at this point we seem to be slowing down rather than speeding up increases in life expectancy which would move us toward longevity escape velocity, where life expectancy increases by (at least) one year per year.

 

--Dean

 

I never understood this idea; life expectancy is increasing at birth while an individual is obviously above that and traveling on a time line. Every year they would capture less of any increase in expectancy. Even if the expectancy was going up by more than a year per year an individual would not achieve "escape velocity" i.e. live forever, at least theoretically. This is the ant on a stretching piece of elastic paradox:

 

https://en.wikipedia.org/wiki/Ant_on_a_rubber_rope

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Good point Martin - just how impactful it will be for any given individual when "longevity escape velocity" (LEV) is achieved for newborns will depend on how old the individual is (and therefore how much damage they've accumulated) and exactly what the treatments are that have been developed to repair damage. Here is a good graph illustrating the potential impact of LEV for people of different ages at the time LEV is reached for newborns:

 

figure12.jpg

 

As can be seen in this example (and it is only an example), if you're 80 or 100 at the time the therapy is developed, it's too late for you. You're inevitably going to die despite the fact that some people (your grandchildren perhaps) will live forever. Sucks for you... If you're 50 or younger (and presumably in reasonably good shape), you're in luck, and have the potential for greatly extended lifespan.

 

--Dean

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