Fig. 1. Percentage of control subjects and patients (young [18–39 yr], middle-aged [40–59 yr], and elderly [60 yr and older]) experiencing postoperative cognitive dysfunction (POCD) at early (hospital discharge) and late (3 months after surgery) testing sessions. *Patient group significantly different from age-matched control subjects , P < 0.001 for all age groups.  § Elderly group significantly different from middle-aged group , P = 0.01. † Elderly patient group significantly different from both young and middle-aged patient groups , P = 0.001.  Symbol Elderly patient group significantly different from elderly control subjects , P < 0.001.