In 1995, an artist named William Utermohlen was diagnosed with Alzheimer’s disease. He continued to make art for the last few years of his life, both as documentation of his daily life and of his decline in cognitive function. Looking through these pieces, you can trace his cognitive changes.
Agatha Christie’s novel “Elephants Can Remember” reveals distinct signs of Alzheimer’s onset, e.g., 20% fewer words or ⅕ of her vocabulary lost; 6 times more use of nonspecific words such as “thing”, and a sharp drop in “idea density”. That novel’s last line is “Maybe it’s OK not to remember.”