Economía demográfica

s of Medicine
The Way We Age Now
Medicine has increased the ranks of the elderly. Can it make old age any easier?
by Atul Gawande
April 30, 2007

T
he hardest substance in the human body is the white enamel of the teeth. With age, it wears away nonetheless, allowing the softer, darker layers underneath to show through. Meanwhile, the blood supply to the pulp and the roots of the teethatrophies, and the flow of saliva diminishes; the gums tend to become inflamed and pull away from the teeth, exposing the base, making them unstable and elongating their appearance, especially the lower ones. Experts say they can gauge a person’s age to within five years from the examination of a single tooth—if the person has any teeth left to examine.

Scrupulous dental care can help avert toothloss, but growing old gets in the way. Arthritis, tremors, and small strokes, for example, make it difficult to brush and floss, and, because nerves become less sensitive with age, people may not realize that they have cavity and gum problems until it’s too late. In the course of a normal lifetime, the muscles of the jaw lose about forty per cent of their mass and the bones of the mandible loseabout twenty per cent, becoming porous and weak. The ability to chew declines, and people shift to softer foods, which are generally higher in fermentable carbohydrates and more likely to cause cavities. By the age of sixty, Americans have lost, on average, a third of their teeth. After eighty-five, almost forty per cent have no teeth at all.

Even as our bones and teeth soften, the rest of ourbody hardens. Blood vessels, joints, the muscle and valves of the heart, and even the lungs pick up substantial deposits of calcium and turn stiff. Under a microscope, the vessels and soft tissues display the same form of calcium that you find in bone. When you reach inside an elderly patient during surgery, the aorta and other major vessels often feel crunchy under your fingers. A recent study hasfound that loss of bone density may be an even better predictor of death from atherosclerotic disease than cholesterol levels. As we age, it’s as if the calcium flows out of our skeletons and into our tissues.

To maintain the same volume of blood flow through narrowed and stiffened blood vessels, the heart has to generate increased pressure. As a result, more than half of us develophypertension by the age of sixty-five. The heart becomes thicker-walled from having to pump against the pressure, and less able to respond to the demands of exertion. The peak output of the heart decreases steadily from the age of thirty. People become gradually less able to run as far or as fast as they used to, or to climb a flight of stairs without becoming short of breath.

W
hy we age is the subjectof vigorous debate. The classical view is that aging happens because of random wear and tear. A newer view holds that aging is more orderly and genetically driven. Proponents of this view point out that animals of similar species and exposure to wear and tear have markedly different life spans. The Canada goose has a longevity of 23.5 years; the emperor goose only 6.3 years. Perhaps animals arelike plants, with lives that are, to a large extent, internally governed. Certain species of bamboo, for instance, form a dense stand that grows and flourishes for a hundred years, flowers all at once, and then dies.

The idea that living things shut down and not just wear down has received substantial support in the past decade. Researchers working with the now famous worm C. elegans (two of thelast five Nobel Prizes in medicine went to scientists doing work on the little nematode) were able to produce worms that live more than twice as long and age more slowly by altering a single gene. Scientists have since come up with single-gene alterations that increase the life spans of Drosophila fruit flies, mice, and yeast.

These findings notwithstanding, scientists do not believe that...