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Rapid increases in numbers reaching 100, but no change in record lifespan

My Times column on how the world’s oldest people
are getting younger:

The two oldest men in the world died recently.
Jiroemon Kimura, a 116-year-old, died in June in Japan after
becoming the oldest man yet recorded. His successor Salustiano
Sanchez, aged 112 and born in Spain, died last week in New York
State. That leaves just two men in the world known to
be over 110, compared with 58 women (19 of whom are Japanese, 20
American). By contrast there are now half a million people over
100, and the number is growing at 7 per cent a year.

For all the continuing improvements in average life expectancy,
the maximum age of human beings seems to be stuck. It’s still very
difficult even for women to get to 110 and the number of people who
reach 115 seems if anything to be falling. According to Professor
Stephen Coles, of the Gerontology Research Group at University of
California, Los Angeles, your probability of dying each year shoots
up to 50 per cent once you reach 110 and 70 per cent at 115.

Female “supercentenarians” — as 110-plus people are called — are
a long way off breaking the record for long life. The record, 122,
was set by Jeanne-Louise Calment in 1997, and the oldest living
person in the world, Misao Okawa, 115 years and 199 days as of
today, would have to live another seven years to overtake that:
meaning Ms Calment’s record will stand for at least 23 years. Ms
Okawa is the only person over 115 alive today, whereas in 1997
there were four.

Japan has more supercentenarians per head of population than
other countries, but not as many as thought a few years ago. After
an investigation in 2010, about 300 very old people, claiming
monthly pensions through their children, were found to be either missing entirely or
dead in their beds for decades. These phantoms included several
over 110.

The lack of any increase in people living past 110 is
surprising. Demographers are so used to rising average longevity
all that they might expect to see more of us pushing the boundaries
of extreme old age as well. Instead there is an enormous increase
in 100-year-olds and not much change in 110-year-olds.

The smidgin of good news for the pension industry, therefore, is
that it seems that human lifespan comes with some sort of a sell-by
date. In this respect we are not like some creatures — tortoises,
sharks, trees — that would apparently go on for ever but for
accidents and illnesses.

Professor Coles has done 11 autopsies on supercentenarians and
finds that most die of congestive heart failure secondary to
“systemic TTR amyloidosis”, a thickening of the blood. The rest
tend to inhale food particles and get pneumonia. It is not really
clear why women live longer than men; probably something to do with
their having a different cocktail of steroid hormones.

Next time you hear some techno-optimist say that the first
person to live to 250, or even 1,000, may already have been born,
remind them of these numbers. The only way to get a person past the
“Calment limit” of (say) 125 will be some sort of genetic
engineering. This might prove to be, if not easy, at least fairly
routine — in technical terms. Fiddling with just a few genes in
worms, fruit flies and mice has enabled scientists to extend their
lifespan, sometimes up to sevenfold. One recent study in Lausanne
found a 50 per cent reduction in the activity of just three genes
on Chromosome 2 increased mouse lifespan by about 250 days, and
kept them healthy longer.

Ethically, however, such a step in human beings is unthinkable,
since it would mean altering the genes of an unborn child without
asking his or her permission. It is hard to imagine any government
allowing such an experiment, with a high probability of unexpected
consequences, let alone anybody finding a team of scientists
prepared to do it. Plus, ethics aside, it is not easy to see where
the demand for such a drastic and expensive step would come from.
Who would actually want their next child to live past 125, let
alone badly enough to go through with it?

All those people who eat wheat germ or special yoghurt or
vitamin supplements in the hope of living for ever are probably
wasting their time. So too are those who practise “caloric
restriction” on the ground that mice live much longer if nearly
starved. Such gaunt folk might get to 100 instead of 90, but they
are not going to get to 120 by such means.

Exercise, too, is nice, but it’s not going to help at extreme
old age. People who walk fast at 75 are more likely to live beyond
85 than those who walk slowly, but cause and effect goes the wrong
way: being likely to live longer makes you a faster walker rather
than vice versa.

It’s still possible there might be a pharmaceutical way of
extending lifespan. The genes that need altering to get flies and
worms to live longer are all part of a nutrient-signalling pathway,
and a drug that affects this pathway has been shown to extend lifespan in flies.
It’s called rapamycin, after Rapa Nui (Easter Island) where it was
first found in soil bacteria. Rapamycin’s molecular targets are
similar in people and flies, so it might work in people too. It is
already used as an anti-cancer agent.

But the latest news is not encouraging, because rapamycin’s
side-effects are unattractive: impaired wound healing, insulin
insensitivity, impaired immunity, cataracts and testicular
degeneration. Dr Linda Partridge, of the Max Planck Institute for
the Biology of Ageing in Cologne, says that separating these
side-effects from the benefits, and working out when people have to
start taking the drug to get any benefit, is the current focus of
work on mice.

In the meantime, those of us who were born before the last
decade of the 20th century can mostly forget about seeing the 22nd
century: there are now just seven people born in the 19th century
known to be still alive. We may live much longer on average than
our grandparents, but there’s not much chance of breaking records.
Just as well when you think about the implications for pensions,
healthcare costs and intergenerational equity.

By Matt Ridley | Tagged:  rational-optimist  the-times