Can We Slow Aging?

People who have a healthy lifestyle and good medical care can expect to live about 80 years, often in good-to-excellent health. As they get older, however, their risk of many diseases, some of them potentially deadly, rises dramatically, doubling roughly every 8 years. Cancer, arthritis, serious problems with thinking and memory, death from flu or COVID-19, and heart attacks all become more common with each decade of life, as do cataracts, hearing problems, skin wrinkles and a long list of other age-related issues. It would be hard to find an 85-year-old with none of these problems, but rare to find a 20-year-old with many of them.

Three kinds of scientific evidence show that aging and the diseases of aging are linked, and that it is not just a coincidence that all these problems develop at roughly the same age. First, some breeds of dogs, usually small ones, live a lot longer than larger breeds, and most diseases of aging appear later in small dogs than in large ones. It therefore makes sense to say that aging runs more slowly in small dogs, delaying most age-related problems and keeping these dogs alive and healthy for longer. The same is true for horses.

Second, data show that most of the age-related problems seen in 80-year-old people also occur in 2-year-old mice, 10–15-year-old dogs, 25-year-old horses, 40-year-old chimpanzees, and 60-year-old albatrosses and elephants. In short, aging runs more slowly in long-lived species.

Third, it has been known for about 90 years that cutting the number of calories that mice or rats eat by 30%–40% can extend their lifespan by about 30%–40% and delay most age-related changes. These “calorie-restricted” lab animals develop many age-related illnesses later, which is why they live so long.

Together, these findings clearly suggest that if researchers could find a way to make aging run more slowly, people would stay healthier for longer and live longer than they do today.

Since the mid-1990s, it has been clear that aging can be slowed. Besides the calorie restriction studies, the next strong evidence came from genetics. In the 1990s, several research groups reported that certain changes, called mutations, in specific genes could dramatically increase lifespan in a species of worm called C. elegans. Mutations that extend the lifespan of laboratory mice were first reported in 1996. Although changing human genes is not practical, these studies raised hopes that it might be possible to find medicines that delay aging and the diseases that come with it.

The first organized search for anti-aging drugs, the Interventions Testing Program (ITP), began in 2003. Each year, the ITP tests about five drugs or natural products to see whether they extend lifespan in mice. So far, 14 drugs have been shown to lengthen the lives of male mice, female mice or both, and for seven of them the increase reached 10% or more. That is a lot: if a similar change could be achieved in people, it would extend healthy human lifespan about three times more than a pill that prevented all adult cancers, or all heart attacks.