Every five years for roughly the last three quarters of a century, life expectancy in industrialized countries has risen by about one year in a phenomenally regular manner. The result has been that not only do people live longer, but a measure of social inequality?variation in the age of death?has decreased.
These changes have been brought about by medicines that either cure a problem or increase the length of time people can live with chronic diseases.
But drugs that prevent aging itself are on the distant horizon, and with them could come dramatic social changes, such as much later ages for everything from puberty to retirement, and massive inequality in life expectancy between those who can afford the life-lengthening compounds, and those who can’t. These changes, in turn, would have a significant impact on the global economy.
“What we’re talking about is not curing diseases… but slowing the aging process itself,” said Alan Cohen, a graduate student at the University of Missouri, who on Friday moderated a panel on the topic at the annual meeting of the American Association for the Advancement of Science in St. Louis.
Aging is essentially the cumulative side effects of metabolism. As human beings age, virtually every physiological measurement doctors and personal trainers can take slows down.
While many scientists agree immortality through pharmacy is not yet worthy of serious debate, and many are cautious of even making hard and fast predictions about life-extending therapies, most agree they are worthy of discussion and tentative planning.
“Over the past couple of years, definitely, aging science has experienced momentum and I think we now know enough to consider the consequences of slowing down aging,” Shin-ichiro Imai, assistant professor in the Department of Molecular Biology and Pharmacology at Washington University.
Molecules Against Aging
The most widely accepted method of increasing life span is to reduce calorie intake to about 60 or 70 percent of normal levels. Obviously, this is not a very easy or pleasurable option for those who try, so the search is on for compounds that mimic the body’s effects of fasting.
As a first step, scientists have identified particular molecules that seem to behave like key gatekeepers in the process of senescence.
An enzyme called Sir2 has been shown to increase longevity in yeast. Increasing the levels of Sir2 by either fiddling with the yeast’s genetics or administering Sir2 like a drug causes yeast cells to live about 30 to 40 percent longer.
The enzyme has the same effect in common laboratory animals such as the worm Caenorhabditis elegans, and the fly, Drosophila melanogaster.
“But we don’t know if it’s quite the same in mammals, which have more complicated metabolism regulation, and different hormones,” said Professor Imai.
“At the moment we are speculating that Sir2 plays a role by regulating the production of hormones in tissues like the pancreatic beta cells. We suspect caloric restriction increases the levels of Sir2 in mammals,” he added. Pancreatic beta cells make and secrete insulin.
A research group at Harvard University is currently working on chemicals to stimulate Sir2 activity. Professor Imai prefers a related approach, which involves increasing levels of a compound called NAD, which will in turn increase Sir2 levels because the two molecules are linked in a biochemical pathway.
Economic Upheaval
The science aside, drugs that slow the rate at which people get old could cause seismic shifts in industrial societies with the money to buy them. Shripad Tuljapurkar, professor at Stanford University, has modeled how anti-aging drugs might affect populations and economies worldwide.
“Maybe we should think about what the consequences of this are before we do it,” said Professor Tuljapurkar.
He has predicted what might happen if such drugs were to become available between 2010 and 2030. Assuming these medications accelerated the ongoing gain in life expectancy by about five times the historical rate, but after 2030 this acceleration ceases, there is likely to be an additional 70 million or 80 million people in the United States in 2050.
(This figure is cut to about 35 million or 40 million if you assume women chose to delay having their first child by a decade over today’s average).
This, in turn, will upset the number of over-65-year-olds compared to those under 20 in the country. This ratio, currently about 0.2, is commonly used in planning for pensions and Medicare.
“If anti-aging drugs have effects similar to our assumptions, the ratio jump will be from 0.2 to 0.4 by 2050. In other words, the burden of supporting people if they retired at 65 would double,” added Professor Tuljapurkar.
A retirement age not far off 85 is likely necessary in order to maintain economic balance.
An older society is also likely to be a more female society. Today there are about four women for every man over the age of 80 in the United States. Given that most surveys still show that women earn less than men doing the same jobs, the pension crisis will be even tougher.
China and India currently represent about a third of the global population. If the same anti-aging drug assumptions are made for these two countries, there would be an additional 400 million people?on top of U.N. predictions for population increase?by 2050.
“That’s an enormous increase,” said Professor Tuljapurkar. “The economic growth in both countries outstrips population growth, but it will soak up the resources they are generating.”
Old Money
Because anti-aging drugs are likely to be highly expensive they may well be available to only the richest, leading to huge differences in life span both across and within nations.
“In Africa we can’t even agree how to allow people to make drugs available more cheaply when it comes to AIDS, so we have almost no chance of doing it with anti-aging therapies,” said Professor Tuljapurkar.
Many other changes would be needed.
“It is very difficult to hold down a job after 65,” he added. “We are going to have to rethink career structures away from simply hierarchies.”
He suggests careers where people can work their way up the ladder and back down the ladder again, without firings, shame, or failure.
