A nationwide study of the long-term prevalence of dementia and its risk factors in the Swedish intensive care cohort

BACKGROUND: Developing dementia is feared by many for its detrimental effects on cognition and independence. Experimental and clinical evidence suggests that sepsis is a risk factor for the later development of dementia. We aimed to investigate whether intensive care-treated sepsis is an independent risk factor for a later diagnosis of dementia in a large cohort of intensive care unit (ICU) patients. METHODS: We identified adult patients admitted to an ICU in 2005 to 2015 and who survived without a dementia diagnosis 1 year after intensive care admission using the Swedish Intensive Care Registry, collecting data from all Swedish general ICUs. Comorbidity, the diagnosis of dementia and mortality, was retrieved from the Swedish National Patient Registry, the Swedish Dementia Registry, and the Cause of Death Registry. Sepsis during intensive care served as a covariate in an extended Cox model together with age, sex, and variables describing comorbidities and acute disease severity. RESULTS: One year after ICU admission 210,334 patients were alive and without a diagnosis of dementia; of these, 16,115 (7.7%) had a diagnosis of sepsis during intensive care. The median age of the cohort was 61 years (interquartile range, IQR 43–72). The patients were followed for up to 11 years (median 3.9 years, IQR 1.7–6.6). During the follow-up, 6312 (3%) patients were diagnosed with dementia. Dementia was more common in individuals diagnosed with sepsis during their ICU stay (log-rank p < 0.001), however diagnosis of sepsis during critical care was not an independent risk factor for a later dementia diagnosis in an extended Cox model: hazard ratio (HR) 1.01 (95% confidence interval 0.91–1.11, p = 0.873). Renal replacement therapy and ventilator therapy during the ICU stay were protective. High age was a strong risk factor for later dementia, as was increasing severity of acute illness, although to a lesser extent. However, the severity of comorbidities and the length of ICU and hospital stay were not independent risk factors in the model. CONCLUSION: Although dementia is more common among patients treated with sepsis in the ICU, sepsis was not an independent risk factor for later dementia in the Swedish national critical care cohort. TRIAL REGISTRATION: This study was registered a priori with the Australian and New Zeeland Clinical Trials Registry (registration no. ACTRN12618000533291).