Unraveling the Relationship Between Delirium, Brain Damage, and Subsequent Cognitive Decline in a Cohort of Individuals Undergoing Surgery for Hip Fracture.

OBJECTIVES: To assess the association between serum S100B levels (a marker of brain damage), delirium, and subsequent cognitive decline.

DESIGN: Substudy of a multicenter randomized controlled trial.

SETTING: Surgical, orthopedic, and trauma surgery wards of two teaching hospitals.

PARTICIPANTS: Individuals aged 65 and older (range 65-102) admitted for hip fracture surgery (N = 385).

MEASUREMENTS: During hospitalization, presence of delirium was assessed daily. S100B was assayed in repeated serum samples. Twelve months after discharge, cognitive decline and mortality were evaluated. Cognitive decline was defined as an increase in Informant Questionnaire on Cognitive Decline Short Form score of 1 standard deviation or more or a decrease in Mini Mental State Examination score of 3 points or more between admission and 12 months after discharge.

RESULTS: Premorbid cognitive impairment was present in 226 (58.7%) participants, and 127 (33.0%) experienced perioperative delirium. Multivariable analysis showed that older age and presence of infection, but not of delirium, were associated with higher S100B levels. Levels were also higher after surgery than before. Of participants with perioperative delirium, 58.6% experienced cognitive decline or death, and only age was a risk factor; 36.5% of participants without perioperative delirium experienced cognitive decline or death in the following year, and higher S100B, premorbid cognitive impairment, and older age were risk factors.

CONCLUSION: In a cohort of older adults with hip fracture, no association was found between serum S100B levels and occurrence of delirium. S100B was associated with cognitive decline or death in the first year after hip fracture only in participants without perioperative delirium. S100B seems to be of limited value as a biomarker of brain damage associated with delirium.