Inflammatory Indices and Their Associations with Postoperative Delirium.

Background: Although the pathogenesis of delirium is poorly understood, increasing evidence supports a role for inflammation. Previously, individual inflammatory biomarkers have been associated with delirium. Aggregating biomarkers into an index may provide more information than individual biomarkers in predicting certain health outcomes (e.g., mortality); however, inflammatory indices have not yet been examined in delirium.

Methods: Four inflammatory markers, C-reactive protein, Interleukin-6, Soluble Tumor Necrosis Factor Alpha Receptor-1, and Chitinase-3 Like Protein-1 (CHI3L1), were measured preoperatively (PREOP) and on postoperative day 2 (POD2) in 548 adults aged 70+ undergoing major noncardiac surgery (mean age 76.7 [standard deviation 5.2], 58% female, 24% delirium). From these markers, four inflammatory indices were considered: 1) quartile summary score, 2) weighted summary score (WSS), 3) principal component score, 4) a well-established inflammatory (LASSO-derived) index associated with mortality. Delirium was assessed using the Confusion Assessment Method (CAM), supplemented by chart review. Generalized linear models (GLM) with a log-link term were used to determine the association between each inflammatory index and delirium incidence.

Results: Among the inflammatory indices, WSS demonstrated the strongest association with delirium: participants in WSS quartile (Q)4 had a higher risk of delirium vs. participants in Q1, after clinical variable adjustment (relative risk [RR], 95% confidence interval [CI] for PREOP: 3.07, 1.80-5.22; and POD2: 2.65, 1.63-4.30). WSS was more strongly associated with delirium than the strongest associated individual inflammatory marker (PREOP CHI3L1 [RR 2.45, 95% CI 1.53-3.92]; POD2 interleukin-6 [RR 2.39, 95% CI 1.50-3.82]).

Conclusions: A multi-protein inflammatory index using WSS provides a slight advantage over individual inflammatory markers in their association with delirium.