Animal studies suggest blood from young donors may have rejuvenating effects for older patients. In a matched cohort study, researchers in Sweden and Denmark examined the potential positive effects of blood from younger donors. Patients receiving red blood cells (RBCs) or plasma from donors less than 25 years old were matched to three controls from older donors. The analysis included over 45,000 plasma recipients and over 136,000 RBC recipients, and was adjusted for recipient age, sex, and the number of transfusions. Donor age was not associated with either 30-day or 1-year mortality after plasma or RBC transfusions. This was consistent across patient subgroups including those with dementia, cardiovascular or cerebrovascular disease. Although clinical trials have not been performed, blood from younger donors does not seem to be associated with patient survival.