Tennis and a longer life

Most exercise research follows people for a season or two. This one followed them for roughly a quarter of a century: 8,577 adults in Copenhagen, first examined in the early 1990s and tracked until 2017. That length is why it keeps being cited — you cannot ask a short study what a habit does to a life.

When the researchers sorted activities by the life-expectancy difference associated with each, the spread was wider than most people expect. A racket sport sat at the top of the table and a health-club routine at the bottom, with something like eight years between them. The gym group were not sedentary. They were exercising, and they still came last.

The authors did not leave that hanging. They noted that the activities clustered at the top all need somebody else — a partner, an opponent, a person expecting you at a particular hour — and suggested the social side of those sports was doing part of the work.

That is a suggestion rather than a result, and the study cannot separate a sport from the people who choose it. Somebody still playing doubles in their fifties may differ from somebody who is not in a dozen ways nobody measured. What this shows is which habits keep company with longer lives — worth knowing, and not the same as knowing why.