Fig. 1. The frequency of postoperative respiratory events is displayed according to the four patient groups defined by the combination of sleep apnea clinical score (SACS) (low/high) and recurrent postanesthesia care unit (PACU) events (no/yes). From a multiple logistic regression analysis, which included SACS group and recurrent PACU events as explanatory variables, the likelihood of postoperative respiratory events was found to be significantly associated with high SACS (odds ratio = 3.5, P = 0.001) and recurrent PACU events (odds ratio = 21.0, P < 0.001).