not sure if anyone's posted this before, but here's a 2016 meta-analysis on this topic: https://artscimedia.case.edu/wp-content/uploads/sites/141/2016/12/22143817/Burgoyne-Sala-Gobet-Macnamara-Campitelli-Hambrick-2016.pdf. There appears to be a real relationship between IQ and chess ability, but it appears to have a small-moderate effect size in general and a still smaller effect size among adult and higher rated (>2000) populations.
I agree with blueemu -- clever, well adjusted people tend to shy away from devoting their lives to games. (I'm a pro poker player btw)
The relationship between chess and IQ is that really clever people don't waste their time playing board games.
"Chess is a sad waste of brains." - Sir Walter Scott