Mild Cognitive Impairment and Risk of Critical Illness

Objectives: Approximately half of ICU admissions are comprised of patients older than 65 years old. Mild cognitive impairment is a common disorder affecting 10-20% of patients in the same age group. A need exists for exploring mild cognitive impairment and risk of critical illness. As mild cognitive impairment may be a contributor to poorer overall health or be a result of it, we sought to determine whether the presence of mild cognitive impairment independently increases the risk of critical illness admissions. Design: Data from the Mayo Clinic Study of Aging were analyzed. All study participants underwent prospective comprehensive cognitive testing and expert panel consensus diagnosis of both cognitive function and clinical state at baseline and subsequent visits. Comparisons were made between those with normal cognitive function and mild cognitive impairment regarding baseline health and frequency of critical illness. Setting: Single-center population-based cohort out of Olmsted County, MN. Participants: All individuals 70-89 years old were screened for prospective enrollment in the Mayo Clinic Study of Aging. Patients with preexisting dementia and ICU admission within 3 years of entry to the study were excluded from this analysis. Interventions: None. Measurements and Main Results: Of 2,425 patients analyzed from the Mayo Clinic Study of Aging, 1,734 patients (71%) were included in the current study. Clinical factors associated with baseline mild cognitive impairment included age, male gender, stroke, and poorer health self-rating. Using a Cox regression model adjusting for these and a priori variables of baseline health, the presence of mild cognitive impairment remained a significant predictor of ICU admission (hazard ratio, 1.50 [1.15-1.96]; p = 0.003). Conclusions and Relevance: The presence of mild cognitive impairment is independently associated with increased critical illness admission. Further prospective studies are needed to analyze the impact of critical illness on cognitive function.