Correlation between complete blood count-derived inflammatory markers and sepsis-associated delirium in older patients: a retrospective analysis of the MIMIC-IV database

Objectives To assess the correlation between complete blood count (CBC)-derived inflammatory markers and sepsis-associated delirium (SAD) risk in older intensive care unit (ICU) patients. Design Retrospective cohort study. Setting ICUs at Beth Israel Deaconess Medical Center (2008–2019), using the Medical Information Mart for Intensive Care IV V.3.0 database. Participants 3412 critically ill patients aged ≥65 years with sepsis. Exclusion: repeated ICU admission, death/discharge within 24 hours, missing delirium assessment or pre-sepsis delirium from non-septic aetiologies. SAD was diagnosed by Confusion Assessment Method for the ICU. Primary outcome measure Incidence of sepsis-associated delirium. Results Among 3412 older sepsis patients, 2092 (61.3%) developed SAD. Significant differences in platelet-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index, systemic inflammation response index, pan-immune-inflammation value and neutrophil-monocyte-to-lymphocyte ratio were observed between SAD and non-SAD groups (all p0.05). Receiver operating characteristic and random forest analyses demonstrated predictive utility; incorporating markers into a baseline model significantly improved discrimination, with MLR providing the largest gain (area under the curve (AUC)=0.716 vs 0.703; ΔAUC=0.013, DeLong test, p<0.001). Conclusion CBC-derived inflammatory markers, particularly MLR, are associated with increased SAD risk in older adults and enhance the performance of a clinical prediction model in this population. Further research is needed to better understand the pathophysiological mechanisms underlying these associations.