Cognitive Impairment Is Associated with Absolute Intraoperative Frontal [alpha]-Band Power but Not with Baseline [alpha]-Band Power: A Pilot Study

Background: Cognitive abilities decline with aging, leading to a higher risk for the development of postoperative delirium or postoperative neurocognitive disorders after general anesthesia. Since frontal [alpha]-band power is known to be highly correlated with cognitive function in general, we hypothesized that preoperative cognitive impairment is associated with lower baseline and intraoperative frontal [alpha]-band power in older adults. Methods: Patients aged [GreaterEqual]65 years undergoing elective surgery were included in this prospective observational study. Cognitive function was assessed on the day before surgery using six age-sensitive cognitive tests. Scores on those tests were entered into a principal component analysis to calculate a composite "g score" of global cognitive ability. Patient groups were dichotomized into a lower cognitive group (LC) reaching the lower 1/3 of "g scores" and a normal cognitive group (NC) consisting of the upper 2/3 of "g scores." Continuous pre- and intraoperative frontal electroencephalograms (EEGs) were recorded. EEG spectra were analyzed at baseline, before start of anesthesia medication, and during a stable intraoperative period. Significant differences in band power between the NC and LC groups were computed by using a frequency domain ([delta] 0.5-3 Hz, θ 4-7 Hz, [alpha] 8-12 Hz, [beta] 13-30 Hz)-based bootstrapping algorithm. Results: Of 38 included patients (mean age 72 years), 24 patients were in the NC group, and 14 patients had lower cognitive abilities (LC). Intraoperative [alpha]-band power was significantly reduced in the LC group compared to the NC group (NC -1.6 [-4.48/1.17] dB vs. LC -6.0 [-9.02/-2.64] dB), and intraoperative [alpha]-band power was positively correlated with "g score" (Spearman correlation: r = 0.381; p = 0.018). Baseline EEG power did not show any associations with "g." Conclusions: Preoperative cognitive impairment in older adults is associated with intraoperative absolute frontal [alpha]-band power, but not baseline [alpha]-band power. Keywords: Aging and cognition, Aging brain, Clinical trials, Cognitive decline, Electroencephalography