The Natural History of Cognitive Impairment in ICU Survivors: A Systematic Review of the Literature
CCCF ePoster library. Honarmand K. Nov 9, 2018; 233436; 110
Dr. Kimia Honarmand
Dr. Kimia Honarmand
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Despite the recent surge in the number of studies assessing cognitive function in ICU survivors, the exact prevalence and natural history (severity, progression, and recovery) of cognitive impairment in this population remains unclear, with prevalence at [insert time point, e.g. ICU discharge] ranging from 9 to 100% (1-3). This wide range in prevalence may be due to multiple factors including: 1) use of diverse cognitive measures with varying psychometric properties, 2) variability in the timing of cognitive assessment relative to recovery from critical illness, and 3) inclusion of multiple patient populations.



We conducted a systematic review of the literature in order to characterize cognitive outcomes in ICU survivors at various time points after recovery from critical illness.



We conducted a systematic search of Ovid Medline, EMBASE, and PsycINFO for potentially relevant, English language articles. We screened titles and abstracts and conducted full-text review of selected articles in duplicate to identify all original studies that reported cognitive function on at least one cognitive domain in adult ICU survivors. We excluded studies that exclusively recruited cardiac arrest or acute neurological injury survivors.



We screened 3351 titles and abstracts and identified 41 relevant studies. Ten studies reported the frequency of subjective cognitive impairment based on patient or family reports at four time points: in hospital, 3 months, 6 months, and variable time points greater than 6 months following discharge. Overall, these studies suggest a lower frequency of subjectively reported cognitive impairment at discharge with a gradual increase over time (Figure 1).


Thirty-two studies reported objective cognitive outcomes based on formal cognitive testing at various time points (Figure 2). The frequency of cognitive impairment was highly variable across studies. The aggregate frequency, weighted by sample size, showed a trend towards declining frequency of cognitive impairment over time. However, 34% still classified as cognitively impaired at 12 months, 46% at 24 months, and 37% at > 24 months, suggesting that at least one-third of ICU survivors experience cognitive impairment long after recovery from critical illness (Figure 2).


Twelve studies included patients with ARDS only and 20 recruited general ICU patients admitted with any diagnosis. Patients with ARDS had a higher prevalence of cognitive impairment than general ICU patients (approximately 80 vs. 50%) up to 3 months following discharge, but this difference equalized at 6 months. Cognitive impairment beyond 12 months has not been assessed in the general ICU group (Figure 3).



Our results show that cognitive impairment affects over half of ICU survivors at discharge and persisting in at least one third of survivors beyond 12 months post ICU discharge. Its prevalence is higher in ARDS patients than in general ICU population. Given improved ICU survival rates and projected increase in utilization of ICU services by aging Canadian population, ICU-related cognitive impairment is evolving into a public health emergency that requires urgent, innovative solutions, especially since overall cognitive function is one of the best predictors of life quality.
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