Whatever happened to those blood transplants people were getting from younger people? Logically it made sense, but I'm guessing after further study it didn't pan out? Or was it just a trend that didn't get any follow up?
There's weak science behind it. Basically it works, but you need to be a crazy person to think that it is a novel way to cheat death. Death remains undefeated.
One, ethics
Two, ethics,
Three, it took something like 10K young people per old person to make it work, and it was at best a proof of concept
Four, ethics
There is still ongoing research and testing. It's at a state where we know it has some effect, but we don't know what exactly it is doing and therefore do not have a clear path to optimization.
https://onlinelibrary.wiley.com/doi/10.1111/acel.70103
https://longevity.technology/news/human-trial-finds-therapeu...