@pratik my dad had a personality change in that age, he became unpleasant to my mother. I once took him to the doctor and happened to see the doctor looking at X-Rays of my fathers brain, I'm definitely not a doctor but my reaction was "oh, oh, that's not good". He died a few months after that, from a fall, and 1-2 years after that I remembered what I had seen and asked for more details. Turned out he had an aggressive type of "brain cancer" that wasn't a tumor but that lived between the regular brain cells. This probably explained the personality changes. So, probably not dementia but still rather unpleasant, especially for my mother (who is perfectly OK ... "brain wise")