['Preclinical studies generated the hypothesis that older stored red blood cells (RBCs) can increase transfusion risks. To examine the most updated and complete clinical evidence and compare results between two trial designs, we assessed both observational studies and randomized controlled trials (RCTs) studying the effect of RBC storage age on mortality.', 'Five databases were searched through December 2014 for studies comparing mortality using transfused RBCs having longer and shorter storage times.', 'Analysis of six RCTs found no significant differences in survival comparing current practice (average storage age of 2 to 3\xa0weeks) to transfusion of 1- to 10-day-old RBCs (OR 0·91, 95% CI 0·77-1·07). RBC storage age was lower in RCTs vs. observational studies (P\xa0=\xa00·01). The 31 observational studies found an increased risk of death (OR 1·13, 95% CI 1·03-1·24) (P\xa0=\xa00·01) with increasing age of RBCs, a different mortality effect than RCTs (P\xa0=\xa00·02).'] Does transfusion of recently donated ( fresh ) red blood cells ( RBCs ) improve survival in comparison with current practice , while safety of the oldest stored units is yet to be established : a meta-analysis?