It seems that Down syndrome and Alzheimer's are hand in glove. For those out of the Down syndrome loop, the 21st chromosome is the one that causes all the problems. Now it is discovered that there is gene on that chromosome that puts our kids at risk for Alzheimer's too. The battle never ends. Women generally, get it earlier and more severely, but less prevalently.
Men get it later in life and less severely, but more men have it.
This is all pretty grim but as with everything that has to do with our children, we will simple take a deep breath, roll up our sleeves, and see what we can do to make the best of things. Diagnosis is difficult for several reasons. Unfortunately symptoms of Alzheimer's have also been reported in 60 other disorders. In addition, some people's low expectations of older adults with Down syndrome leads to neglect in some situations. To avoid a missed diagnosis, the best defense is to maintain good records and have periodic evaluations to detect change in behavior, change physically, or change in abilities.