Outcome of HLA–identical sibling transplantations by birth order. (A) Graft survival of 6062 living HLA–identical sibling donor kidney allografts by birth order. (i) Donor younger than recipient. (ii) Donor older than recipient. Ten-year graft survival hazard ratio (HR) of older versus younger donor = 1.06 (95% confidence interval, 0.94-1.20; P = .37). (B) Graft survival of 1704 allogeneic HSCTs from HLA–identical sibling donors for aplastic anemia by birth order. (i) Donor younger than recipient. (ii) Donor older than recipient. Ten-year patient survival HR of older versus younger donor = 1.126 (95% confidence interval 0.914-1.388; P = .265).