Risk factors for preoperative and postoperative delirium in elderly patients with hip fracture.

OBJECTIVES: To evaluate risk factors for preoperative and postoperative delirium.

DESIGN: Prospective cohort study.

SETTING: Departments of orthopedic surgery in two Norwegian hospitals.

PARTICIPANTS: Three hundred sixty-four patients with and without cognitive impairment, aged 65 and older.

MEASUREMENTS: Patients were screened daily for delirium using the Confusion Assessment Method. Established risk factors and risk factors regarded as clinically important according to expert opinion were explored in univariate analyses. Variables associated with the outcomes (P<.05) were entered into multivariate logistic regression models.

RESULTS: Delirium was present in 50 of 237 (21.1%) assessable patients preoperatively, whereas 68 of 187 (36.4%) patients developed delirium postoperatively (incident delirium). Multivariate logistic regression identified four risk factors for preoperative delirium: cognitive impairment (adjusted odds ratio (AOR)=4.7, 95% confidence interval (CI)=1.9-11.3), indoor injury (AOR=3.6, 95% CI=1.1-12.2), fever (AOR=3.4, 95% CI=1.5-7.7), and preoperative waiting time (AOR=1.05, 95% CI=1.0-1.1 per hour). Cognitive impairment (AOR=2.9, 95% CI=1.4-6.2), indoor injury (AOR=2.9, 95% CI=1.1-6.3), and body mass index (BMI) less than 20.0 (AOR=2.9, 95% CI=1.3-6.7) were independent and statistically significant risk factors for postoperative delirium.

CONCLUSION: Time from admission to operation is a risk factor for preoperative delirium, whereas low BMI is an important risk factor for postoperative delirium in hip fracture patients. Cognitive impairment and indoor injury are independent risk factors for preoperative and postoperative delirium.