So interesting about the clock! We had a lot of varieties of demential to deal with. FIL never diagnosed, but was the sort who would diligently read the newspaper and was unable to have any kind of conversation about what he had read. But he was 100% capable to the end of having pleasant conversations and could play chess to the end. I met him when he was in his late 50s or early 60s. He was still working but I was always surprised at how un-intellectual he seemed. My MIL on the other hand was always supersmart and take charge. Sadly she succumbed to early on set dementia. She was let go from her work presumably because she was beginning to make questionable decisions. She fell prey to all sorts of scams before we figured out what was going on and made the phone unlisted, and sent all the mail to a PO box so she couldn’t open it.
My father diagnosed with Alzheimer’s just drifted away. He never lost the ability to have what seemed like a sensible conversation, but he remembered nothing. I had to remind the kids not to get mad when he asked where they were in school more than once! My mother was diagnosed with Parkinson’s (though my SIL thought the actual symptoms were much more in line with Lewe’s Body dementia). Her doctor said she was the most self aware person he had ever met. She had lots of visual hallucinations, but was always aware that they weren’t real and often she could send them away. It was remarkable. It was only in the last few months of her life that she stopped enjoying watching movies and the like.