Fig. 3

Cumulative survival curves using Cox proportional hazard regression model with a time-dependent covariate. The cumulative survival curves for the low (< 0.5), medium (0.5–1.0), and high (≥ 1.0) plasma-to-red blood cell transfusion ratio groups, which were estimated using the Cox proportional hazard regression model for non-geriatric group (A) and geriatric group (B) patients. The hazard ratio for 28-day mortality was controlled for age, sex, injury severity score, Revised Trauma Score, injured region, and hospital type. The plasma-to-RBC ratios at 4 h and 24 h were treated as time-dependent covariates