What is young blood / plasma exchange, and does it actually work?

Young blood or plasma exchange is built on the idea that ageing can be reversed by adding young blood components to old blood. The concept comes from so-called parabiosis experiments in mice: surgically connecting the circulatory systems of a young mouse and an old mouse showed that the organs of the old mouse rejuvenated noticeably. Those effects have been demonstrated causally in animal experiments, but that is not yet evidence that it works in humans.

A key finding is that simply adding young factors is not the whole story -- it also matters enormously to remove harmful factors from old blood. Exposing young muscle cells to old blood strongly accelerated their ageing in mouse studies. As a result, research is increasingly focused on plasma exchange, in which aged proteins are removed without the need for donor blood. Mouse studies show that this returns the protein profile to a younger state^1,2.

In mouse studies of Alzheimer's disease, young plasma improved spatial memory and partially restored lost synaptic proteins. However, the characteristic plaques of Alzheimer's disease did not decrease. A young bone marrow transplant kept synaptic connections in the brain intact and reduced inflammation in brain immune cells in mice. Whether any of this applies to humans is unknown and is being investigated in early clinical studies^3,4,5,6,7,8.

Commercial companies are already selling 'young blood transfusions' to people, while evidence for safety or efficacy is lacking. One publication from a company with a commercial interest bases its conclusions about ageing reversal partly on anecdotal evidence, the weakest form of scientific evidence. That warrants extra caution. Anyone paying for this is buying a product with no clinical substantiation and unknown risks.