Critical illness at extreme age: outcomes and clinical characteristics of centenarian ICU admissions in Australia and New Zealand

The centenarian population is increasing globally, yet data describing intensive care unit (ICU) outcomes in this age group remain limited. We aimed to describe the clinical characteristics and outcomes of centenarians admitted to ICU and to evaluate the performance of commonly used severity-of-illness scores for mortality prediction. This retrospective cohort study included all index ICU admissions of patients aged ≥100 years recorded in the Australian and New Zealand Intensive Care Society Adult Patient Database between 2010 and 2024. The primary outcome was in-hospital mortality. Secondary outcomes included ICU mortality, discharge destination, and survival at 6 months, 1 year, and 2 years. Competing-risk regression was used to assess factors associated with mortality. Discrimination of SOFA, APACHE III, and ANZROD was evaluated using the area under the receiver operating characteristic curve (AUROC). Among 460 centenarians, the median age was 100.9 years (IQR 100.3–102.0), and 67.2% were female. Surgical admissions predominated (67.2%). Treatment limitation orders were documented in 33.9% of patients, whereas invasive mechanical ventilation was used in 10.3%. In-hospital mortality was 13.7%, and ICU mortality was 3.9%, with most deaths occurring early during hospitalisation. Among hospital survivors, 54.1% were discharged home, with a median post-discharge survival of 21.9 months. Acute illness severity was strongly associated with mortality in adjusted competing-risk models, whereas chronological age was not. ANZROD demonstrated superior discrimination for ICU mortality (AUROC 0.90) and hospital mortality (AUROC 0.82) compared with SOFA and APACHE III. In this binational cohort, ICU admission among centenarians was infrequent and occurred in a highly selected population. Treatment limitation orders were common and mechanical ventilation was uncommon; approximately half of hospital survivors were discharged directly home. In-hospital mortality was relatively low and more strongly associated with acute illness severity than with chronological age. These findings support individualised clinical decision-making regarding ICU admission at extreme age rather than age-based exclusion.