PURPOSE: A significant portion of the elderly population is affected by cognitive impairment. However, there are few studies investigating the incidence of cognitive impairment prior to ICU admission in a population based sample.
METHODS: Data from the previously described Mayo Clinic Study of Aging (Roberts, et al., Neuroepidemiology 2008;30:58-69) was analyzed for prevalence of critical illness defined as admission or transfer to an intensive care unit. This prospective cohort consisted of patients aged 70-89 enrolled between 2004 to 2008, residing in Olmsted County, Minnesota, with no previous ICU admissions within 3 years of the start of the study. Study subjects were evaluated and followed every six months using the Clinical Dementia Rating Scale, Functional Assessment Questionnaire, neurological evaluation, and neuropsychological testing. An expert panel consensus diagnosis of normal cognition, MCI, or dementia was made at baseline and at each assessment. ICU admission dates for each patient were obtained by review of the electronic record. Subjects with baseline cognitive status before ICU admission were compared to those without ICU admissions.
RESULTS: Of 2487 patients recruited into the study, 387 had at least one ICU admission during 2 years of follow-up. Cognitive impairment was identified in 455 participants during their baseline evaluation and 35 patients went on to develop cognitive impairment prior to an ICU admission. The incidence of cognitive impairment prior to ICU admission is significantly higher among patients admitted to an ICU 35% (136 out of 387) compared to patients without ICU admissions 18% (319 out of 1733) (P<0.001). Compared to patients without cognitive impairment, those with cognitive impairment are older (85 vs. 82, p<0.001), more likely to be male (69% vs. 53%, p=0.002), and have higher APACHE III score(69 vs.63, p=0.05) on admission but similar ICU mortality(6% vs 4%, p=0.42).
CONCLUSIONS: The incidence of pre-existing cognitive impairment remains high among patients admitted to the ICU. ICU mortality is similar among patients with and without cognitive impairment.
CLINICAL IMPLICATIONS: Cognitive impairment is a risk factor for ICU admission.
DISCLOSURE: The following authors have nothing to disclose: David Teeters, Teng Moua, Michelle Biehl, Ognjen Gajic, Ron Peterson, Sean Caples, Guangxi Li
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