Lack of clinically relevant correlation between subjective and objective cognitive function in ICU survivors: a prospective 12-month follow-up study

BackgroundCognitive impairment and psychological distress are common in intensive care unit (ICU) survivors. Early identification of affected individuals is important, so intervention and treatment can be utilized at an early stage. Cognitive Failures Questionnaire (CFQ) is commonly used to screen for subjective cognitive function, but it is unclear whether CFQ scores correlate to objective cognitive function in this population.MethodsBetween 2014 and 2018, 100 ICU survivors aged 18-70years from the general ICU at the Karolinska University Hospital, Solna, were included in the study. Out of these, 58 patients completed follow-up at 3months after ICU discharge, 51 at 6months, and 45 at 12months. Follow-up included objective cognitive function testing using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and subjective cognitive function testing with the self-rating Cognitive Failures Questionnaire (CFQ), as well as psychological self-rating with the Post-Traumatic Stress Symptoms Scale-10 (PTSS-10) and Hospital Anxiety and Depression Scale (HADS).ResultsThe prevalence of cognitive impairment as measured by four selected CANTAB tests was 34% at 3months after discharge, 18% at 6months, and 16% at 12months. There was a lack of significant correlation between CANTAB scores and CFQ scores at 3months (r=-0.134-0.207, p>0.05), at 6months (r=-0.106-0.257, p>0.05), and at 12months after discharge (r=-0.070-0.109, p>0.05). Correlations between CFQ and PTSS-10 scores and HADS scores, respectively, were significant over the follow-up period (r=0.372-0.710, p <= 0.001-0.023). In contrast, CANTAB test scores showed a weak correlation with PTSS-10 and HADS scores, respectively, at 3months only (r=-0.319-0.348, p=0.008-0.015).ConclusionWe found no clinically relevant correlation between subjective and objective cognitive function in this cohort of ICU survivors, while subjective cognitive function correlated significantly with psychological symptoms throughout the follow-up period. Treatment and evaluation of ICU survivors' recovery need to consider both subjective and objective aspects of cognitive impairment, and subjective reports must be interpreted with caution as an indicator of objective cognitive function.