It is inevitable. The muscles weaken. Hearing and vision fade. We get wrinkled and stooped. We can’t run, or even walk, as fast as we used to. We have aches and pains in parts of our bodies we never even noticed before. We get old. It sounds miserable, but apparently it is not. A large Gallup poll has found that by almost any measure, people get happier as they get older, and researchers are not sure why.

Well, I’m certainly happier than I was in my 20s, or even 30s. But I’m not really feeling any physical effects of aging yet. I suggest, however, that this is a good argument for life extension — if people get happier as they live longer, and if that remains true even as their bodies fall apart, they’re likely to be happier still if they remain healthy.