If you’re over 40, working more than 25 hours a week could be affecting your intelligence, new research suggests

I went back to work halftime at 6 months and did that for 2 months before going fulltime.  The worst part was trying to keep track of conversations in group meetings. It took at least a year before I could process the information flow fast enough to be able to contribute intelligently.
http://www.bbc.com/capital/story/20160714-is-full-time-work-bad-for-our-brains
Good luck trying to get your bosses to allow 25 hour work weeks.