Gaming

It's far more likely you just aren't spending as much time playing games and so your skill has wained:

https://www.vintageisthenewold.com/game-pedia/do-you-get-worse-at-gaming-as-you-get-older#:~:text=If%20anything%2C%20reaction%20time%20and,as%20good%20at%20a%20game.

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This and other studies show that the 'reaction time' decrease when aging that gamers like to site is mostly inconsequential and has almost zero real impact (certainly not any impact that can't be overcome from just practice), even in reaction heavy games like Counter Strike.

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Video games are one of the most 'elastic' forms of competition there is aside from playing cards. Muscles wane, physical ability wanes but your mind mostly stays building upon itself (unless you suffer from an illness/disease).