Abstract

Absolute lymphocyte count has often been proposed as a practical prognostic variable in critical illness. In older adults, however, immunosenescence and long-term immune remodeling may lower baseline lymphocyte levels and weaken their relationship with outcomes. We therefore examined whether lymphopenia at ICU admission predicts 28-day mortality in geriatric patients and whether it improves commonly used prognostic models. We undertook a retrospective cohort analysis of 202 consecutive ICU admissions of patients aged ≥ 65 years in a tertiary university hospital between January and December 2019. Admission lymphopenia was defined as an absolute lymphocyte count < 1100 × 10³/μL. The primary outcome was 28-day mortality. Independent predictors were assessed using multivariable logistic regression, and discriminative performance was evaluated using ROC curve analysis. Lymphopenia was present in 76.2% of patients and showed no significant association with 28-day mortality (p = 0.209). Mortality was independently related to ward admission, higher APACHE II and Charlson Comorbidity Index scores, lower Glasgow Coma Scale score, and the need for mechanical ventilation and renal replacement therapy. Adding lymphopenia to multivariable models did not improve discrimination (AUROC 0.752 – 0.897; all p > 0.9). In geriatric ICU patients, lymphopenia at admission is frequent but does not independently predict short-term mortality and does not provide incremental value beyond established severity indicators. These findings support prioritizing validated clinical severity scores and organ support variables over isolated immune-cell counts when stratifying mortality risk in older ICU populations.

Key words: Lymphopenia, geriatrics, intensive care, 28-day mortality, prognostic marker