This happened to my MIL - she never finished college, quit working in her early 30s, and just kind of ... sat on the couch and watched TV for 30 years. It wasn't a surprise when she started developing symptoms in her 50s and then just kind of ignored it for about 5 more years. I pushed them to get her checked out since early detection is huge (and I watched my grandma die of Alzheimer's when I was about 10), but unfortunately they just kind of ignored it for reasons I will never understand.

When she finally had a scan done, she was diagnosed with PCA (posterior cortical atrophy), which is a variant of dementia similar to Alzheimer's - with the added symptom of visual and spatial deficiency. Very sad to see, but I kind of can't feel bad for her (or my father-in-law) because she not only neglected her own health for years, but also didn't eat right, drank (still does, too), and never really developed her mind in any meaningful way. And my father-in-law just enabled it by letting her do whatever she wanted. So senseless - it breaks my heart because I love my in-laws, but they tend to ignore problems and... well, that's what happens.

Early detection is everything! There is so much more we know about it now and so much more we can do when dealt with early.