Longevity may be a mathematical, genetical trend, scientists say
Copyright ) 1998 Nando.net
Copyright ) 1998 Reuters News Service
WASHINGTON (May 7, 1998 6:56 p.m. EDT http://www.nando.net) -
Longevity is in.
More people are living longer and are expected to continue living
longer well into the 21st century, a team of 14 international
scientists said Thursday, adding the trend also includes
insects and cars.
"The major take is longevity is going up, more rapidly than we can
explain," said Thomas Johnson, professor of behavioral genetics at the
University of Colorado at Boulder.
"Humans can't live forever, but there is no real limit."
Johnson is one of the researchers from institutions in Europe, the
United States and Mexico who found that 15 percent of the world
population in 2025 will be 60 or older.
This figure is up from just nine percent in 1997, according to the
study published in the journal Science.
Led by James Vaupel of Max Plank Institute for Demographic Research
in Rostock, Germany, researchers studied the life expectancies of
people in developed and developing nations by using a
technique called biodemographics, a mix of biology, demography and
statistics.
After gathering data from various countries, they found the
countries projected to have the highest percent of people over 60 will
be Japan and Italy, with 33 percent.
By 2025 32 percent of Germany's population will be 60 or older,
they predicted, and in Sweden 29 percent of the population will be
60-plus.
The percent of over-60s in the United States is expected to climb
to 25 percent of the population from 17 percent in 1997, the
scientists said.
In developing countries like India and Mexico, the elderly
population is expected to increase over the quarter-century to at
least 12 percent.
There are reasons for the increase of longevity in America and
elsewhere.
It's in part due to the aging of the baby-boom generation, better
medical care and nutrition. But there is another factor, the
scientists said: once people make it to old age, they hang in
there -- especially women.
"Since the early 1970s female death rates in Japan have declined at
annual rates of about 3 percent for octogenarians (80-year-olds) and
two percent for nonagenarians (90-year-olds)," the
researchers wrote.
"Mortality among octogenarians and nonagenarians has been low in
the United States." They also found that the population of
100-year-olds of various developed countries has doubled every 10
years since 1960.
This is perplexing, they said. Perhaps genetics were a factor, or
acquired characteristics such as better nutrition.
But the trend does not hold just in people. Wasps, a nematode worm,
baker's yeast and four species of fruit flies also tend to live longer
as the species survive. It even happens to cars.
So the researchers suggest that some higher process -- mathematics,
for example, might be responsible. A deceleration in mortality could
simply be a general property of complex systems.
There may be ways to speed up this process. Johnson, who worked on
nematodes and roundworms, said that when a gene known as ag-1 is
eliminated in nematodes, they live longer -- almost twice
as long.
"I was incredulous," he said. "I replicated 14 times." With ag-1,
nematodes normally live about three weeks, Johnson said, but without
it they lived five to six weeks.
It is easier to delete genes from worms than from people, but
Johnson plans to try the trick on mice next.
By JOHN POIRIER, Reuters News Service
----------------------
One humorous consequence of American centenarians doubling every
decade is that they will overtake the population as a whole around
2150 -- although by then I guess we'll be worrying about the
exploding number of quarter-millenarians.
Being a mathematician, I find the notion that longevity has a
mathematical cause particularly charming. :-)
Rich Schroeppel rcs@cs.arizona.edu
Received on Fri May 8 15:06:25 1998
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