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Objective To test the hypothesis that duration of delirium in the intensive care unit (ICU) is an independent predictor of long-term cognitive impairment after critical illness requiring mechanical ventilation. Design Prospective cohort study. Setting Medical ICU in a large community hospital in the United States. Patients Mechanically ventilated medical ICU patients who were assessed daily for delirium while in the ICU and underwent comprehensive cognitive assessments 3 and 12 months after discharge. Measurements and Main Results Of 126 eligible patients, 99 survived ≥3 months post-critical illness; long-term cognitive outcomes were obtained for 77 (78%) patients. Median age was 61 years, 51% were admitted with sepsis/ARDS, and median duration of delirium was 2 days. At 3-and 12-month follow-up, 79% and 71% of survivors had cognitive impairment, respectively (with 62% and 36% being severely impaired). After adjusting for age, education, preexisting cognitive function, severity of illness, severe sepsis, and exposure to sedative medications in the ICU, increasing duration of delirium was an independent predictor of worse cognitive performance—determined by averaging age- and education-adjusted T-scores from nine tests measuring seven domains of cognition—at 3-month (p = 0.02) and 12-month follow-up (p = 0.03). Duration of mechanical ventilation, alternatively, was not associated with long-term cognitive impairment (p = 0.20 and 0.58). Conclusions In this study of mechanically ventilated medical ICU patients, duration of delirium was independently associated with long-term cognitive outcomes, representing a potentially modifiable predictor of this common public health problem.

Background Critical illness is associated with cognitive impairment, but mental health and functional disabilities in general intensive care unit (ICU) survivors are inadequately characterized and there are a paucity of data regarding the relationship between age and delirium and these outcomes. Methods In this prospective, multisite cohort study, we enrolled medical/surgical ICU patients with respiratory failure or shock, collected detailed demographics and in-hospital variables, and assessed survivors at 3 and 12 months with measures of depression, posttraumatic stress disorder (PTSD) and functional disability. We used linear and proportional odds logistic regression to examine the independent associations between age and delirium duration versus mental health and functional disabilities. Findings We enrolled 821 patients with a median (interquartile range) age of 61 (51, 71), assessing 448 patients and 382 patients 3 and 12 months after discharge. At 3- and 12-month follow-up, 37% (149/407) and 33% (116/347) of subjects reported at least mild depression, driven primarily by somatic rather than cognitive symptoms. Depressive symptoms were common even among those with no proxy reported history of depression, reported at 3- and 12-month follow-up by 30% (76/255) and 29% (62/217) of these individuals. At either follow-up assessment, only 7% (27/415, 24/361) of subjects had symptoms consistent with PTSD. Disabilities in basic activities of daily living (ADLs) and instrumental activities of daily living (IADLs) were present in 32% (139/428) and 26% (108/422) of individuals at 3 months and in 27% (102/374) and 23%(87/372) at 12 months. Mental health and functional difficulties were prevalent in young and old patients. Although older age was frequently associated with mental health and functional disabilities, no consistent association was observed between delirium and these outcomes. Interpretation In contrast with early single-center reports, data from this large, multicenter investigation reveal depression is much more common than PTSD after critical illness and is driven by somatic symptoms indicative of physical disabilities rather than by cognitive symptoms. Poor mental health and functional disability were common, and persistent in up to a quarter of patients.