I took up the piano again after retiring - around 50 years after passing only grade 2, so it was more or,less a case of starting again from scratch.
It was definitely harder. As a child I would memorise pieces without even trying - it's infinitely more difficult now, and even then I can only manage it with certain pieces (with very regular rhythms and clearly defined sections.)
I also found playing scales with both hands very difficult at first, whereas as a child I never had a problem.
On the plus side, after several years both my playing and sight reading are light years better than they were (sight reading was virtually non existent!) and I'm sure that forging all those new connections in my brain (e.g.knowing instantly what that chord is and where to find it, instead of having to think each time) can only have been beneficial to ze little grey cells, as Poirot calls them.
It's maybe 8 years now since I finished an OU degree (Humanities) which of course was a lot of work, but compared with the piano I didn't find it any harder to write essays or revise for exams, than I did in my youth. In fact I enjoyed the courses rather more than those I studied long ago.