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.