Originally Posted by
Nonsensical 
In horribly depressing news, my Downs Syndrome brother (age 48) is starting to exhibit signs of dementia. Really common for people with Down Syndrome to develop dementia, but we were hoping he would dodge that fate. He has not been formally diagnosed, but the symptoms seems pretty clear.
Sorry to hear about your brother. I am a scientist at the national institute on aging and our lab studies Alzheimer's disease (among other neurodegenerative diseases). Not sure if you know this or not, but I found it really interesting - It is nearly 100% of Down's syndrome patients that develop Alzheimer's disease, and the reason is that the APP gene, which produces the protein that ends up making Amyloid beta plaques (a diagnostic criteria for Alzheimer's) is on chromosome 21 - the chromosome that Downs patients have 3 instead of 2.
It is believed that all modern Downs patients will develop Alzheimer's if they live long enough. It used to be that a lower percentage developed it because so many died younger before the critical heart surgery was routinely performed.
I hope this doesn't sound cold as far as your brother is concerned. I very much understand the devastation of that disease both professionally and personally. I just thought you might be interested in that information. Or maybe you already knew.
Anyway, here's hoping better treatments are available soon. By the way, the most reliable treatment we have seen in the lab (with mice) is exercise. Same has been seen in humans.