Age-related sex differences in intensive care treatment and outcomes: a nationwide cohort study

Reported differences in treatment and mortality between male and female patients in the ICU are inconsistent. Previous studies suggest that age might influence sex differences, partly explaining earlier discrepancies. This study aimed to compare patient characteristics, care intensity, and mortality between male and female ICU patients while examining potential age-varying sex differences. All adult (≥18 yr) ICU patients between 2012 and 2024 were identified in the Swedish Intensive Care Registry. Multivariable logistic regression models, adjusted for age and Simplified Acute Physiology Score 3, investigated associations between patient sex and 30-day mortality, continuous renal replacement therapy, and invasive ventilation. Analyses included the entire cohort and six diagnostic subgroups. To describe the varying effect of sex across ages, a multivariable logistic regression model, using natural cubic splines, allowed age to interact with sex. This study included 303 875 ICU patients (median interquartile range age: 67 51-76 yr; 42.8% female). Crude mortality was higher in male patients (odds ratio OR 0.94, confidence interval CI 0.92-0.95). In multivariable models, female sex was associated with higher 30-day mortality (OR 1.03, CI 1.01-1.05). Male patients were more likely to receive continuous renal replacement therapy and invasive ventilation. Female patients had lower mortality risk at younger ages and higher mortality risk at older ages. Although males constitute a larger proportion of ICU patients and receive more advanced treatments, females have higher adjusted mortality. This is nuanced by age-specific variations, which underscore the complexity and necessity of considering age when evaluating sex-based differences in ICU outcomes.