https://academic.oup.com/eurjpc/advance-article/doi/10.1093/eurjpc/zwaf267/8128214
association between fitness and an outcome not expected to be causally affected is examined (e.g. random accidents
You can already see the flaw in their paper. A more fit person is more active. Going out more. Being exposed to more random accidents. The safest place to be is laying in bed all day. If you go out and run, if you go to the gym, any activity, you have more chance for random accidents…
You have the finding back-to-front
“The researchers found that men with the highest fitness levels had a 53 per cent lower risk of dying in random accidents.”
The paper suggests there may be some factor or combination that causes physical fitness, low disease mortality, and low accident risk - rather than physical fitness itself causing low disease mortality