Age-dependent changes in the power spectrum conflate composite scores to assess brain frailty.

Objective: Evaluating age-related dependencies in the electroencephalogram (EEG) during induction of general anesthesia and their impact on composite scores used to assess frailty.

Methods: A composite score was derived from spectral edge frequency, total power, alpha power, and the effect-site concentration (Ce) of propofol. All these parameters are influenced by age, brain health, and dosage and speed of drug administration. Correlation coefficients and variance inflation factors were used to determine multicollinearity. Differences in the spectral EEG features of patients with "high" and "low" composite scores were assessed by the area under the receiver operator characteristic curve (AUC) as the statistical test.

Results: The EEG features, total power and alpha power, were strongly correlated ( = 0.82). But alpha power ( = 0.17) and total power ( = 0.2) were only weakly correlated with propofol, indicating a weak model. Additionally, the composite score showed a moderate negative correlation with age ( = -0.44). We also observed significant and strong (AUC  0.3) differences in total power and the power of all EEG bands except gamma between patients with a "high" and a "low" score before loss of responsiveness (LOR).

Conclusion: Patient age significantly influences EEG-based parameters within the score. Importantly, significant differences in spectral EEG features between the groups were already observable before LOR. These differences could allow for early assessment of a patient's brain state and to titrate anesthetic dose before LOR. The study also shows that age should be considered as it can drive models for "frailty".

Significance: Age moderately influenced all subcomponents and should consequently be factored into score interpretation.