Neutrophil-lymphocyte ratio as a predictor of delirium in older internal medicine patients: a prospective cohort study

BACKGROUNDS: Delirium is a common neuropsychiatric syndrome in older hospitalized patients. Previous studies have suggested that inflammation and oxidative stress contribute to the pathophysiology of delirium. However, it remains unclear whether neutrophil-lymphocyte ratio (NLR), an indicator of systematic inflammation, is associated with delirium. This study aimed to investigate the value of NLR as an independent risk factor for delirium among older hospitalized patients. METHODS: We conducted a prospective study of 740 hospitalized patients aged ≥ 70 years in the geriatric ward of West China Hospital of Sichuan University. Neutrophil and lymphocyte counts were collected within 24 h after hospital admission. Delirium was assessed on admission and every 48 h thereafter. We used the receiver operating characteristic analysis to assess the ability of the NLR for predicting delirium. The optimal cut-point value of the NLR was determined based on the highest Youden index (sensitivity + specificity − 1). Patients were categorized according to the cut-point value and quartiles of NLR, respectively. We then used logistic regression to identify the unadjusted and adjusted associations between NLR as a categorical variable and delirium. RESULTS: The optimal cut-point value of NLR for predicting delirium was 3.626 (sensitivity: 75.2 %; specificity: 63.4 %; Youden index: 0.386). The incidence of delirium was significantly higher in patients with NLR > 3.626 than NLR ≤ 3.626 (24.5 % vs. 5.8 %; P < 0.001). Significantly fewer patients in the first quartile of NLR experienced delirium than in the third (4.3 % vs. 20.0 %; P < 0.001) and fourth quartiles of NLR (4.3 % vs. 24.9 %; P < 0.001). Results from the multivariable logistic regression models showed that NLR was independently associated with delirium. CONCLUSIONS: NLR is a simple and practical marker that can predict the development of delirium in older internal medicine patients. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-021-02284-w.