This is where the field known as the biology of aging is moving — to develop drugs that will increase life span and what researchers refer to as health span, the period of life when people are able to live independently and free from disease.

Dr. Kirkland said that at least six drugs had been written up in peer-reviewed journals and that he knew of about 20 others that appear to affect life span or health span in mice. The goal is to see if those benefits can be translated into humans to increase their longevity, “to find interventions that we can use in people that might, say, make a person who’s 90 feel like they’re 60 or a person who’s 70 feel like they’re 40 or 50.”

Other researchers are studying centenarians, seeking to understand whether certain genes have carried them past 100 years old and kept them in good health.

“Everybody knows someone who’s 60 who looks like he’s 50, or someone 60 who looks 70,” said Dr. Nir Barzilai, the director of the Institute for Aging Research at the Albert Einstein College of Medicine who is currently studying centenarians and their children. “Intuitively, we understand that we age at different rates, so the question is, really, ‘What’s the biological or genetic difference between those who age quickly and those who age slowly?’ ” Drugs that mimic the effect of those genes might be beneficial to the rest of the population not born with them.