Animal models suggest that blood from younger donors may provide revitalizing benefits, but findings from observational cohort studies on this topic have been inconsistent. Investigators in Scandinavia recently performed a retrospective cohort study following 968,264 red blood cell (RBC) transfusion recipients for 10 years. Since multiple transfusions can confound results, researchers used multiple approaches to carefully analyze the survival of transfusion recipients based on donor age and sex. After adjusting for the number of transfusions and taking into account non-linear relationships of variables, donor age and sex were not associated with mortality among RBC transfusion recipients. This study also highlights the importance of methodologic considerations in the analysis of retrospective cohort studies.