Host Response in Critically Ill Patients Aged 65 Years or Older: A Prospective Study

Background: The host response plays a critical role in the progression of all critical illnesses, especially in the aging population. With aging becoming a global phenomenon, understanding changes in the host response among elderly patients can provide valuable insights for diagnosis and treatment in the ICU. Methods: This study included all patients aged 65 and older admitted to our geriatric intensive care unit (GICU). Demographic, clinical, and medication data were extracted from electronic medical records. The primary outcome was in-hospital mortality, while secondary outcomes included hospital length of stay (LOS) and ICU stay duration. We employed the generalized additive mixed model for analysis and utilized nomogram analysis to build a predictive mortality model. Results: A total of 1204 patients, with a median age of 75 years and a maximum age of 110 years, were admitted to the GICU. Host response biomarkers were notably lower in patients over 85 years. White blood cell (WBC) count, lactate dehydrogenase (LDH), interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-alpha) were positively associated with mortality, while a higher platelet-tolymphocyte ratio (PLR) was inversely related to mortality. Lymphocyte count was identified as a significant risk factor for mortality (RR = 1.2181). Elevated host response biomarkers were inversely associated with both hospital and ICU LOS. The predictive model integrating these biomarkers exhibited strong predictive performance for mortality. Conclusion: Our findings underscore the significant impact of aging on host response in critically ill patients. Older patients, particularly those over 85, exhibited lower biomarker levels and higher mortality rates. The predictive model developed from inflammatory, immune, and coagulation markers demonstrated robust prognostic utility, aiding in the evaluation of critically ill elderly patients.