Neuropsychological profiles of an elderly cohort undergoing elective surgery and the relationship between cognitive performance and delirium

Objectives: To examine baseline (preoperative) neuropsychological test performance in a cohort of elderly individuals undergoing elective surgery and the association between specific neuropsychological domains and postoperative delirium.

Design: Ongoing prospective cohort study.

Setting: Successful Aging after Elective Surgery Study.

Participants: Elderly adults (N=300) scheduled for elective (noncardiac) surgery.

Measurements: Neuropsychological testing, including standardized assessments of memory, divided and sustained attention, speed of mental processing, verbal fluency, working memory, language, and an overall measure of premorbid cognitive functioning, was performed 2 to 4 weeks before surgery. The relationship between the individual neuropsychological tests and delirium status was examined using linear regression, adjusting for age, sex, and education.

Results: Study participants were generally highly educated (mean years of education 15.0±2.9), with minimal or no cognitive impairment (mean Modified Mini-Mental State Examination score 93.2 out of 100). After adjustment, participants who developed postoperative delirium had performed significantly lower preoperatively on measures of speed of mental processing and divided attention (Trail-Making Test Part B, mean difference 17.55, P=.02), category fluency (animal naming, mean difference -1.94, P=.01), sustained visual attention (Visual Search and Attention, mean difference -3.19, P<.001), and working memory with new learning and recall (Hopkins Verbal Learning Test-Revised Total mean difference -0.53 to -0.79, P<.01).

Conclusion: Individuals who later develop delirium have lower scores on tests evaluating the areas of complex attention, executive functioning, and rapid access to verbal knowledge or semantic networks at baseline. Future studies to better understand how the cognitive profiles identified may predispose individuals to developing delirium may help pave the way to greater understanding of the mechanisms of delirium.