Delirium: An Independent Predictor of Functional Decline After Cardiac Surgery

OBJECTIVES To determine whether patients who developed delirium after cardiac surgery were at risk of functional decline. DESIGN Prospective cohort study. SETTING Two academic hospitals and a Veterans Affairs Medical Center. PARTICIPANTS One hundred ninety patients aged 60 and older undergoing elective or urgent cardiac surgery. MEASUREMENTS Delirium was assessed daily and was diagnosed according to the Confusion Assessment Method. Before surgery and 1 and 12 months postoperatively, patients were assessed for function using the instrumental activities of daily living (IADL) scale. Functional decline was defined as a decrease in ability to perform one IADL at follow-up. RESULTS Delirium occurred in 43.1% (n=82) of the patients (mean age 73.7 +/- 6.7). Functional decline occurred in 36.3% (n=65/179) at 1 month and in 14.6% (n=26/178) at 12 months. Delirium was associated with greater risk of functional decline at 1 month (relative risk (RR)=1.9, 95% confidence interval (CI)=1.3-2.8) and tended toward greater risk at 12 months (RR=1.9, 95% CI=0.9-3.8). After adjustment for age, cognition, comorbidity, and baseline function, delirium remained significantly associated with functional decline at 1 month (adjusted RR=1.8, 95% CI=1.2-2.6) but not at 12 months (adjusted RR=1.5, 95% CI=0.6-3.3). CONCLUSION Delirium was independently associated with functional decline at 1 month and had a trend toward association at 12 months. These findings provide justification for intervention trials to evaluate whether delirium prevention or treatment strategies might improve postoperative functional recovery.