The study in Nature Medicine showed the old mice injected with young plasma did better on classic behavioral tests, such as the maze water test. Researchers observed positive structural changes in their brains, including a 20-50% increase in the neuroplasticity network.

Human trials testing the efficacy of young-to-old blood transfusions are currently underway in the US. The randomized, double-blind study involves 18 people aged 50-90 with moderate to severe Alzheimer’s. For one month each patient will receive a weekly plasma injection from donors aged 30 and under, in addition to a four-week course of saline as a placebo, with six weeks between the treatments.

Wyss-Coray and others have set up a private company, Alkahest, in order to fund such studies. Much of the money for the initial trial was donated by the family of a Chinese billionaire, who suffered from Alzheimer’s and appeared to improve temporarily after receiving a blood transfusion.