Transfusions seem unlikely to work at this point based on evidence to date, probably because the factors involved are very short-lived. E.g. transfusions failed to move the needle in mice:
There is a human trial for transfusion of young blood to Alzheimer's patients but this is probably not going to tell us much, because it is so specific, and because the mouse transfusions didn't work.
It could also be a feedback process - components in older blood induce responses in younger organ tissue that releases components into younger blood that is then transferred to the older organism
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4215333/
There is a human trial for transfusion of young blood to Alzheimer's patients but this is probably not going to tell us much, because it is so specific, and because the mouse transfusions didn't work.
http://www.newscientist.com/article/mg22329831.400-young-blo...