The long-term conditional mortality rate in older ICU patients compared to the general population.

Background: Understanding how preexisting comorbidities may interact with a critical illness is important for the assessment of long-term survival probability of older patients admitted to the ICU.

Material and methods: The mortality after a first ICU admission in patients ≥ 55 years old registered in the Swedish Intensive Care Registry was compared to age- and sex-matched individuals from the general population with a landmark after 1 year. The comparison was adjusted for age, sex, and baseline comorbidity using Cox regression.

Results: The 7-year study period included 140 008 patients, of whom 23% were 80 years or older. Patients surviving the first year remained at an increased risk compared to the general population, but much of this difference was attenuated after adjustment for baseline comorbidity (HR, 1.03; 95% CI 1.02-1.04). Excluding cardio-thoracic ICU admissions, the increased risk remained slightly elevated (adjusted HR, 1.15; 95% CI 1.13-1.16). Also, the subgroup ≥ 75 years old surviving the first year returned to a mortality rate comparable to the general population (HR, 0.98; 95% CI 0.96-0.99). Stratified by admission diagnosis an increased mortality rate remained beyond the first year for acute-on-chronic respiratory failure (adjusted HR, 1.47; 95% CI 1.36-1.58) but not for other respiratory causes (adjusted HR, 1.03; 95% CI 0.99-1.07) or admission for septic shock (adjusted HR, 1.04; 95% CI 0.95-1.13). No substantial increased mortality rate was notable beyond the first year for other admission diagnoses.

Conclusion: Older ICU patients that survive the first year after an ICU admission return to a mortality rate close to that of the general population having similar baseline comorbidity, but variability is seen depending on the ICU admission diagnosis. Trial registration ClinicalTrials.gov ID: NCT06234709, date 02/01/2024.