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

## TL;DR

This study shows that age affects EEG-based composite scores used to assess brain frailty during anesthesia, with differences detectable before patients lose responsiveness.

## Contribution

The study reveals that age-related changes in EEG parameters can confound composite scores for brain frailty assessment.

## Key findings

- Total power and alpha power in EEG were strongly correlated but weakly linked to propofol concentration.
- Patients with high and low composite scores showed significant differences in EEG power before loss of responsiveness.
- Age moderately correlates with the composite score and should be considered in its interpretation.

## Abstract

•Age can conflate composite scores containing EEG-related parameters.•Patients with high composite scores showed differences in EEG-related parameters compared to those with low scores.•Differences are detectable already before loss of responsiveness that could allow adjustments of anesthesia navigation.

Age can conflate composite scores containing EEG-related parameters.

Patients with high composite scores showed differences in EEG-related parameters compared to those with low scores.

Differences are detectable already before loss of responsiveness that could allow adjustments of anesthesia navigation.

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

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.

The EEG features, total power and alpha power, were strongly correlated (ρ = 0.82). But alpha power (ρ = 0.17) and total power (ρ = 0.2) were only weakly correlated with propofol, indicating a weak model. Additionally, the composite score showed a moderate negative correlation with age (ρ = -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).

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”.

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