Down Syndrome and Alzheimer's

From the psychology of aging course that most of us took last year, I recall learning about how there is a connection between Down syndrome and Alzheimer's disease. We really only touched on the subject so I thought it would be a good idea to look into it further. I have found that people who have Down syndrome are much more likely to develop Alzheimer's disease, and they do so at a younger age. Adults with Down syndrome are likely to develop the plaques and tangles associated with Alzheimer's disease as young as 3 or 4 years old. Their brains are able to repair the damage for a few decades and the common symptoms are likely to appear a few decades earlier then they do in the average adult. I read an article by USA Today that somewhat explained how people with Down syndrome aren't susceptible to numerous diseases that come with aging.  They are unlikely to develop heart disease despite the majority of them being overweight, or even hard cancers even though they show the effects of aging much earlier than a person without Down syndrome. Doctors are still working on figuring out what is happening on the 21st chromosome that does these things but makes them more susceptible to Alzheimer's disease. Last May, a few scientists discovered genes on chromosome 21 that inhibit the growth of blood vessels. This may have an affect on the development of Alzheimer's. By the age of 65, 75% of people with Down syndrome will also have dementia.
http://www.usatoday.com/news/health/2010-03-22-down22_CV_N.htm