Cognitive and brain reserve and the risk of postoperative delirium in older patients: analysis of data from a prospective observational study

Abstract

Background: Cognitive and brain reserve theories suggest that aspects of neural architecture or cognitive processes modify the effect of neuropathological processes on cognitive outcomes. Although frequently studied in the context of dementia, reserve in delirium is understudied.

Methods: Using data from a prospective observational study, we examined the association of three markers of brain reserve (head circumference, MRI-derived brain volume, and leisure time physical activity), five markers of cognitive reserve (education, vocabulary, cognitive activities, cognitive demand of lifetime occupation, and interpersonal demand of lifetime occupation), and the risk of postoperative delirium in 566 older adults (age ≥70 years) free of dementia undergoing scheduled surgery.

Findings: 135 (24%) of 566 patients developed delirium during the postoperative hospital stay. Of the reserve markers examined, only the Wechsler Test of Adult Reading was associated with the risk of delirium. A 0·5 SD better performance on the Wechsler Test of Adult Reading was associated with a 38% reduction in delirium risk (adjusted risk ratio of 0·62, 95% CI 0·45-0·85; p=0·01).

Interpretation: Most markers of reserve failed to predict delirium risk. The exception to this is the Wechsler Test of Adult Reading. Our findings suggest that the reserve markers that are important for delirium might be different from those thought to be important for dementia.