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Scientific prospects for extending human life span are good

Conditions related to genetics, diet, lifetime exposure to toxins, and other factors limit longevity.

Aug. 2010, Article 1

Right now, the average span of life for women in the U.S. is about 88 years, and 82 years for men. But a few of us (somewhat less than 1 in 1000) will live to 100, and a very small percentage of those will make it to 110. The really interesting thing is that the percent of those living to 100 ("centenarians") has been rising sharply over the last half century, and there are no indications that this trend is abating. Most of the centenarians are women, since women outlive men by 4 – 8 years in all developed countries.

The record for human longevity, 123 years, is held by Jeanne Calment, of Paris, France. Her apartment in central Paris was so sought after (because rents are controlled, but available properties there are extremely scarce) that a man paid Jeanne Calment the equivalent of $60,000 for the right to succeed her in that apartment when she died. At the time of this transaction, the man was 63 and Mme. Calment was 87. Needless to say, the man never spent even one day living in the home for which he had invested his savings; Jeanne Calment outlived him by several decades.

How long could people live, in the future? Are there things we can do when we are young that will affect our health in late life, and ultimately our life spans? We certainly know many things to avoid, that would make us less fit. Smoking, excessive sun exposure, obesity, and physical inactivity all take their toll, and raise the likelihood of illness or death from a host of debilities and diseases. Less well known, exposure to a variety of toxic chemicals (PCBs, lead, cadmium, radon etc.) reduces life expectancy. All these dangers are inferred from epidemiologic studies of humans – observing ages at death of people who had reported their recollections of previous exposures.

There are limitations to the confidence we can or should place in conclusions reached in that way. Do people who smoke also tend to take more risks in other activities? Do those who live near polluting factories also tend to have reduced access to medical care? It isn't entirely clear that the factors that seem to be tightly linked to diseases or early death are in fact responsible for those outcomes. Studies with animals are easier to interpret and can (if well designed) point to the true causes. In later articles in this series, we will look closely at what scientists have been able to learn from animals, about fundamental processes that govern aging and life span — lessons that almost certainly apply to humans.

Our best guess is that we will, within the next 20 – 30 years, be able to take some sort of pills to increase our life expectancy so that the average approaches the longest life spans we see today. Basically, these will be pharmacologic fixes for the deficiencies in the rest of us, to fulfill our maximal life-span potential. The more distant future may hold other interventions that block the root causes of aging, and thus have a potential for serious life extension. There will probably be limits to what can be achieved in that way, because the very process of living involves burning food for energy, and that is believed to be the source of most of the molecular damage that limits our survival. It is far too early to predict what those limits will turn out to be.

Robert J.S. Reis
Udupa Chair of Gerontologic Research
Professor, Depts. Of Geriatrics, Biochemistry & Molecular Biology, and Pharmacology/Toxicology
University of Arkansas for Medical Sciences

Copyright © 2010 RJR Reis. Used with permission.