Estimating the Association Between Cognitive Impairment and Delirium in Patients with Neck of Femur Fractures

Introduction:

Over 70,000 hip fractures are sustained annually in the UK (1), with the majority of these occurring in older adults. These patients are at high risk of delirium, with reported incidence between 14.4-29.3% (2,3). Perioperative delirium is associated with increased mortality, length of hospital stay and institutionalization. Delirium is more common in patients with pre-existing cognitive impairment. We aimed to estimate the magnitude of this association in a real-world setting to aid risk stratification and perioperative management. 

Methods:

We performed a retrospective analysis of 118 patients (mean age = 81.8 years; 70.3% female) using de-identified, routinely collected data from a locally approved clinical audit conducted in a major trauma centre. Pre-existing cognitive impairment was defined by a documented history of cognitive impairment prior to admission. Delirium was defined as a 4AT score ≥4 (where available) in combination with either a documented diagnosis of delirium or documented clinical features of delirium. Odds ratios and 95% confidence intervals were estimated using logistic regression, adjusting a priori for age and sex. 

Results:

Among 118 patients admitted with neck of femur fractures, 29.7% (n=35/118) had pre-existing cognitive impairment and 22.9% (n=27/118) had a documented delirium. Delirium occurred in 45.7% (16/35) of patients with cognitive impairment, compared with 13.3% (11/83) of those without cognitive impairment. Cognitive impairment was associated with increased odds of delirium (crude OR 5.39, 95% CI 2.16-14.00). Following adjustment for age and sex, the association remained substantial (adjusted OR 4.59, 95% CI 1.79–12.28, p=0.002).

Conclusions:

Pre-existing cognitive impairment is strongly associated with perioperative delirium in patients presenting with neck of femur fractures. Patients presenting with a neck of femur fracture and cognitive impairment require close monitoring to identify and manage perioperative delirium.