Very much so. I'm genetically high IQ and used to have a very sharp mind and memory. Was in gifted and talented at a good school despite putting in no effort whatsoever. Nowadays my short-term memory is non-existent and my concentration levels are nil. I zone out performing the simplest tasks and have to double and treble check everything. I can't remember names or details of anything, I'm like an old man. I can't concentrate on anything that isn't a short Youtube video, and even then I get bored and click off after a minute or two 90% of the time. I love films but don't have the patience to watch any, I've watched maybe 10 new films in the past few years.
My brain isn't totally fried, however. I did some quizzing with the family a while back and was surprised how well I did. Answers came to me much slower than they used to but I've also accumulated some extra knowledge. I think part of getting older is that you accumulate more knowledge but your recall and reflexes become worse. Something like your long-term memory becoming better but your short-term memory becoming worse. But in my case it's been expedited hugely.
Reading is probably the simplest fix for this. If you read for at least 30 minutes per day and get through at least 10-20 books per year your brain will be in decent shape, provided there's a decent mix of some challenging stuff in there. Social interaction is essential as well. Isolation destroys your brain and faculties. The latter has been the main problem for me. I live in complete isolation and daydream incessantly. And I never read, despite being good at it. I've read 10-20 books in my lifetime, almost all of those during a pretentious period in my late teens/early 20s.