Do you live longer from playing tennis or squash?
For tennis there are indications of a substantial gain in life expectancy, but for squash the evidence is entirely absent. If you have to choose based on what is currently known, tennis wins that comparison easily.
Tennis is the only racket sport for which direct longevity figures are available. In a large Copenhagen study, in which people were followed for an average of 25 years, tennis players had a life expectancy almost 10 years higher than that of completely inactive people. That is the highest figure of all the sports included in that research. Badminton came second, with just over 6 extra years. Squash was not measured separately in this study.
In another large study of more than 95,000 international elite athletes, racket sports (tennis and badminton combined) also performed well: male athletes lived up to nearly 6 years longer than the general population, and women approximately 3 years. Squash was not included as a separate category in that study, so a direct comparison with squash is not possible.
That near-10-year figure for tennis sounds impressive, but it calls for nuance. An older classic study, which looked at physical activity in general without distinguishing by sport, found only 1 to 2 extra years of life among people who were sufficiently active. That difference suggests that the high tennis scores are partly explained by who plays tennis: people with more social contacts, better access to sport, or other favourable life circumstances. The researchers of the Copenhagen study themselves name social interaction as a possible explanatory factor.
For squash, no longevity figures are simply available on the basis of the studies at hand. Whether squash scores comparably to tennis or badminton is therefore unknown. At present, tennis is the racket sport with the strongest evidence base for a longer life expectancy.
The answer rests on two large observational studies in which people were followed for many years (a Copenhagen city study and an international sports dataset), supplemented by a classic American alumni study and an analysis of tennis champions. All four are studies in which people were followed over time; no cause-and-effect relationship has been demonstrated. Squash is absent as a category in all sources provided. For women in the international athletes study, the figures were based on a small minority of the dataset, which makes those results less reliable.
Is 75 minutes of exercise per week already enough?
75 minutes of vigorous exercise per week already delivers almost the maximum benefit for your lifespan. On top of that, make sure you do not sit for long uninterrupted periods during the day, as that is a separate risk.
Why do some cells stop dividing as you age?
Cells stop dividing because their chromosome tips wear down and they accumulate DNA damage: a protective mechanism that in later life becomes harmful precisely because the stalled cells build up. Treatments that address this are still under active investigation and are not ready for self-application.