Study of the top 5 newspapers found "144 articles focused on either or both Biden’s and Trump’s ages or mental acuities in the period studied, with 67% focused just on Biden’s age or mental acuity and only 7% on just Trump’s."
It's clear bias, but we haven't been beating that drum for generations.
https://www.mediamatters.org/washington-post/top-newspapers-fixate-bidens-age