Actually top level OTB chess ability degrades notably past 50 with a few notable exceptions (Korchnoi, Smyslov). Sure the decline starts a bit later than regular sports but still it is significant.

That is why when Rausis(https://www.chessgames.com/perl/chessplayer?pid=14248) rating was approaching 2700 in his 50s everyone was very suspicious.

It is partially due to the incredible levels of stamina required to stay on top of the game for 4-6 hours.

Also as Kramnik said when he was retiring, you start making strange(read wrong) decisions suddenly.