Are there family studies or clinical trials to determine if Alzheimer's is hereditary?

Nursetiff asked...

I have a family history of Alzheimer's - my paternal great grandmother and my paternal grandfather had Alzheimer's, and now one of my paternal aunts has a rare form of dementia. My grandparents had late onset - diagnosed in their 70's & 80's, but my aunt was only 58 years old when she was diagnosed. Are their any family studies or clinical trials, or help of any kind for families with an extensive history?