> Two main results emerge. First, average skills increase strongly into the forties before decreasing slightly in literacy and more strongly in numeracy. Second, skills decline at older ages only for those with below-average skill usage. White-collar and higher-educated workers with above-average usage show increasing skills even beyond their forties. Women have larger skill losses at older age, particularly in numeracy. [emphasis mine]

So, it seems like workers with above-average usage of literacy and numeracy continue to increase their ability, while those in fields that don’t emphasize those would need some kind of mental “exercise”.

(I also note that some commenters here are rushing to add more cognitive work to their daily routine through additional studies, but I wonder if they’d be better off focusing on commonly neglected areas like physical activity.)