First, this involves plasma, not whole blood. This is inferred in the article, but not made clear. Technically, the process is called plasmapherisis and has been tried in the past, to little apparent success. If anyone is old enough to remember, there was a clinic on 5th Ave. (lower 5th, near NYU, the students of which were where the plasma allegedly came from) that offered plasmapherisis as an anti-aging treatment in the mid to late 60's (remember Dr. Orenreich and his rejuvenated beagles?). There were only anecdotal reports of success and I think the clinic stopped offering the procedure in the early 70's. Plasmapherisis was a common treatment for Psoriasis in the 50's and 60's and some patients reported feeling more youthful after treatments. The clinic was originally a dermatology clinic and is, AFAIK, still around (may have moved though). It's proprietor was also known as the inventor of the modern hair transplant and I notice that he is still alive in his mid-nineties.
Tens of millions of blood transfusions and plasma transfusions are done every year around the world. Surely, if it was effective; someone would have noticed the correlation many years ago and we would all be doing it. Doctors are smart like that.
Doctors, might of noticed a change but as they wouldn't know / remember what age the plasma came from, most of the time it'll be 25+ age donations so might be tricky to spot. I've got 14years before I get to 60, hopefully we'll have hard data and the price will come down, maybe even it'll save so much money down the line it'll be government funded. Maybe life expectancy would drop hugely ie 10years, I'd take a better life for 10years than 30years of misery any day, and people not living as long would be very good for the younger generation, so a good trade off