Risk Factors and 120-Day Functional Outcomes of Delirium After Hip Fracture Surgery: A Prospective Cohort Study Using the UK National Hip Fracture Database (NHFD).

Objectives: To identify risk factors of postoperative delirium among hip fracture patients with normal preoperative cognition, and examine associations with returning home or recovery of mobility.

Design: Prospective cohort study.

Setting And Participants: We used the National Hip Fracture Database (NHFD) to identify patients presenting with hip fracture in England (2018-2019), but excluded those with abnormal cognition [abbreviated mental test score (AMTS) < 8] on presentation.

Methods: We examined the results of routine delirium screening performed using the 4 A's Test (4AT), to assess alertness, attention, acute change, and orientation in a 4-item mental test. Associations between 4AT score and return home or to outdoor mobility at 120 days were estimated, and risk factors identified for abnormal 4AT scores: (1) 4AT ≥4 suggesting delirium and (2) 4AT = 1-3 being an intermediate score not excluding delirium.

Results: Overall, 63,502 patients (63%) had a preoperative AMTS ≥8, in whom a postoperative 4AT score ≥4 suggestive of delirium was seen in 4454 (7%). These patients were less likely to return home [odds ratio (OR), 0.46; 95% CI, 0.38-0.55] or regain outdoor mobility (OR, 0.63; 95% CI, 0.53-0.75) by 120 days. Multiple factors including any deficit in preoperative AMTS and malnutrition were associated with higher risk of 4AT ≥4, while use of preoperative nerve blocks was associated with lower risk (OR, 0.88; 95% CI, 0.81-0.95). Poorer outcomes were also seen in 12,042 (19%) patients with 4AT = 1-3; additional risk factors associated with this score included socioeconomic deprivation and surgical procedure types that were not compliant with National Institute of Health and Care Excellence guidance.

Conclusion And Implications: Delirium after hip fracture surgery significantly reduces the likelihood of returning home or to outdoor mobility. Our findings underline the importance of measures to prevent postoperative delirium, and aid the identification of high-risk patients for whom delirium prevention might potentially improve outcomes.