Comment by petercooper

I'm not the OP and I imagine all cases are different, but my dad was a software developer who had early cognitive decline in his 60s (he died of vascular dementia recently) and he used to talk about it a lot. He said it was like his tolerance for complexity kept closing in.

Where he could once hold an entire system and its details in his head (almost an essential skill in the 80s/90s), he could only instead focus on smaller pieces at a time. Any new tooling or approaches that came along, he was fascinated to hear about them, but no longer felt able to pick them up. He could still solve algorithmic problems and debug "in the small", but it was like he had to do math on a Post-it note where once he had a huge sheet of paper.