Depression in older adults undergoing hip surgery increases postoperative delirium risk

Depressive symptoms were associated with underlying Alzheimer’s disease pathology and postoperative delirium in older adults who underwent hip fracture repair, according to a study published in American Journal of Geriatric Psychiatry.

“Previously, clinically significant depression had been shown to be associated with postoperative delirium, but the data on whether mild depressive symptoms are also associated with postoperative delirium have been mixed,” Esther S. Oh, MD, PhD, associate professor in the division of geriatric medicine and gerontology at the Johns Hopkins University School of Medicine, told Healio Psychiatry. “In addition, the underlying mechanism of the association between depressive symptoms and postoperative delirium remained unclear. The goal of the study was to determine the association between depressive symptoms and postoperative delirium, and whether this association may be due to underlying Alzheimer’s disease in some of the patients undergoing hip fracture surgery.”

Oh and colleagues analyzed preoperative data via the 15-item Geriatric Depression Scale (GDS-15) of 199 patients aged 65 years or older who underwent hip fracture surgery and participated in a randomized clinical trial. Participants also completed a standard Mini-Mental State Exam (MMSE) to identify mental impairment and provided cerebrospinal fluid (CSF), which was assayed for amyloid-beta 40, 42, total tau and phosphorylated tau₁₈₁.

Results showed risk for postoperative delirium increased 13% for every one-point increase in GDS-15 score, adjusted for baseline cognition, age, sex, race education and CSF Alzheimer’s disease biomarkers (OR = 1.13; 95% CI, 1.02-1.25). The researchers noted an inverse association between higher GDS-15 scores and both CSF amyloid-beta 42/total tau and amyloid-beta 42/phosphorylated tau₁₈₁, with lower ratios indicative of greater Alzheimer’s disease pathology. Results of an analysis to pinpoint the strongest delirium predictors among 18 variables showed GDS-15 exhibited the highest classification accuracy for postoperative delirium and better predicted delirium than both cognition and Alzheimer’s disease biomarkers.

“We did not find that Alzheimer’s disease as measured by two biomarkers accounted for all the association between depressive symptoms and postoperative delirium,” Oh said. “This is most likely because in a surgical population such as the hip fracture population, which tends to be older (average age, 82 years), there are other disease processes, such as vascular disease in the brain, that contribute to the overall brain vulnerability that leads to delirium.”