Association between admission hemoglobin-to-red blood cell distribution width ratio and stroke-associated pneumonia risk in acute ischemic stroke: effect modification by diabetes status

Objective This study aimed to assess the relationship between admission hemoglobin-to-red blood cell distribution width ratio (HRR) and stroke-associated pneumonia (SAP) risk in patients with acute ischemic stroke (AIS), and to explore whether this association is modified by diabetes status. Methods In this retrospective study of 1051 patients with AIS admitted within 72 hours of symptom onset, we first visualized the shape of the association between admission HRR and SAP risk using a generalized additive model (GAM). Subsequently, multivariable logistic regression was used to assess this association, adjusting for available confounders, yielding adjusted odds ratios (ORs) and 95% confidence intervals (CIs). The stability of this association was rigorously tested through extensive subgroup and sensitivity analyses. Results A linear negative association was observed between HRR and SAP risk. In the fully adjusted model, HRR was inversely associated with SAP risk (adjusted OR = 0.75; 95% CI: 0.64, 0.87; p < 0.001). A significant interaction was detected between HRR and diabetes status (p for interaction = 0.01). Stratified analysis showed that the inverse association was present in non-diabetic patients (OR = 0.69; 95% CI: 0.59, 0.81; p < 0.001) but not in diabetic patients (OR = 0.97; 95% CI: 0.77, 1.21; p = 0.76). Conclusion Admission HRR is inversely associated with SAP risk in AIS patients. This association is modified by diabetes status (p for interaction = 0.01), with the inverse association attenuated in diabetic patients. SAP risk stratification strategies may need to account for diabetes status.