The role of C-reactive protein as a risk marker of postoperative delirium in older hip fracture patients: a prospective cohort study

Abstract Background: Postoperative delirium (POD) after hip fracture surgery is a common and serious neuropsychiatric syndrome that leads to higher morbidity and mortality. Current predictive models of delirium are based on clinical factors that can be subjective and imprecise. In this study we investigated the association between serum C-reactive protein (CRP) and the occurrence of POD in older hip fracture patients, and whether CRP predicted POD better than a clinical model. Methods: Patients aged ≥75 years admitted for surgical repair of an acute hip fracture were recruited. A Comprehensive Geriatric Assessment (CGA) was performed at admission and blood samples were collected preoperatively in the absence of delirium. Delirium was assessed daily until discharge with the 4-AT. We compared serum CRP levels between patients with and without POD and examined the association between CRP and delirium severity. Mann-Whitney U and Spearman tests were used for group comparisons. Results: Sixty patients were included, of whom 21 (35%) developed POD. Serum CRP levels were significantly higher in patients who developed delirium ( p = 0.011), but no significant association was found between CRP and delirium severity ( p = 0.079). In a multiple regression model including the most representative clinical variables associated with delirium (age, comorbidity, grip strength, frailty, infection and pre-existing cognitive impairment) and CRP, cognitive impairment ( p = 0.003) and infection ( p = 0.001) were the best predictors of POD. Conclusions: Although higher levels of serum CRP were significantly associated with POD in older hip fracture patients, pre-existing cognitive impairment and infections were the most important risk factors for POD.