Interesting article on fivethirtyeight (from 2017):

...To get some insight into how chess skill might decline with age, I downloaded the most recent FIDE rating list, from the beginning of August. This lists ranks all the players registered with the game’s international governing body according to their Elo rating.1 The end result was a data set with more than 280,000 players and their respective ratings. These are all the players currently rated by FIDE, although some of them, such as Kasparov, are flagged as “inactive,” meaning that they haven’t played a rated game in a year or more. (To estimate a given player’s age, we subtracted his or her birth year from 2017.)

The result is shaped like a large floating apostrophe of mortality. After a steep increase in players’ early years (youth is wasted on the young), the estimated trend in ratings peaks just after age 38, before beginning a long, slow, irreversible and depressing decline (kinda like real life). ...