PURPOSE: As elderly patients greater than 65 account for nearly half of ICU admissions and have increased prevalence of mild cognitive impairment (MCI), we sought to study prospectively the prevalence of MCI in initially cognitively normal individuals after critical illness.
METHODS: To allow for post ICU follow-up of at least 2 years, our analyzed cohort involved 2487 patients between 2004 and 2008 from the previously described Mayo Clinic Study of Aging, a prospective cohort of 2719 Olmsted County residents aged 70-89 enrolled on October1, 2004. We excluded an additional 367 participants with ICU admission within 2 years prior to initial enrollment date, those with initial baseline MCI or dementia, and those subsequently lost to follow-up or with incomplete data. At enrollment and subsequent interval evaluation every 6-12 months per the Mayo Clinic Study of Aging protocol, standardized laboratory, imaging, and neurocognitive testing was done with consensus neurocognitive diagnoses updated for each participant. Correlating ICU data was gathered from the electronic records.
RESULTS: Prospective follow-up of cognitively normal participants admitted to the ICU was available for 164 individuals (mean age 81(75-84), 71 male (43%)). Only 7 (4%) developed MCI after critical illness in the 2 year follow-up period with a mean time to MCI of 188 (65-564) days. Severity of illness as assessed by APACHE III scores was statistically lower (MCI: 52 IQR, 41-58; no MCI: 61 IRQ 52-73) for those with subsequent MCI than those without, with no difference between length of ICU or hospital stay as noted on index ICU admission (mean length of stay in ICU 1.1 (0.9 to 2.8) vs 1.1 days(0.9 to 1.7) P=0.93, hospital length of stay 3.2(1.4-6.9) vs. 4.7 days (2.7 to 6.9) P=0.5 ). Use of mechanical ventilation for each group was 3 out of 7 (43%) in those with subsequent MCI vs 60 out of 157 (38%) in those without.
CONCLUSIONS: Critical illness does not appear to accelerate the incidence or prevalence of MCI in cognitively normal patients followed carefully pre and post critical illness with neurocognitive assessment up to two years.
CLINICAL IMPLICATIONS: Neurocognitive decline after critical illness may reflect already present subclinical disease.
DISCLOSURE: The following authors have nothing to disclose: Teng Moua, Guangxi Li, Alex Teeters, Michelle Biehl, Ognjen Gajic, Ron Petersen, Sean Caples
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