Stress hyperglycemia ratio as a risk factor for delirium in older intensive care unit patients: a retrospective cohort study

Delirium is a severe neurocognitive complication in older ICU patients, associated with poor outcomes. The stress hyperglycemia ratio (SHR), reflecting acute hyperglycemia relative to chronic glycemic control, may predict adverse outcomes. This study examined the association between SHR and delirium in older ICU patients. This retrospective cohort study used MIMIC-IV data. We included 2,644 patients (≥ 65 years) with complete glucose data and delirium assessments. SHR was calculated as admission fasting glucose divided by estimated average glucose derived from HbA1c. Delirium was identified using CAM-ICU. Multivariable logistic regression adjusted for demographics, vital signs, laboratory parameters, comorbidities, and medications. Nonlinear relationships were explored using restricted cubic splines. Delirium incidence increased across SHR tertiles: T1 32.3%, T2 40.5%, T3 52.0% ( p < 0.001). In fully adjusted models, continuous SHR remained independently associated with delirium (OR = 1.44; 95%CI:1.13–1.82; p = 0.003). The highest versus lowest tertile showed elevated risk (OR = 1.63; 95%CI:1.28–2.09; p < 0.001; trend p < 0.001). Inflection point analysis identified a threshold at SHR = 1.530, below which the association was stronger. Subgroup analysis revealed a more pronounced association in patients with cerebrovascular disease (OR = 1.81; 95%CI:1.17–2.79; p for interaction = 0.048). Elevated SHR is independently associated with increased delirium risk in older ICU patients, regardless of diabetic status. SHR may serve as a practical biomarker for early identification of high-risk individuals, facilitating targeted prevention.