Increased mortality in patients with standard EEG findings of 'diffuse slowing'

We aimed to confirm the association between slow brain wave activity typically described as "diffuse slowing" on standard electroencephalogram (EEG) and patient outcomes, including mortality.

This retrospective study was conducted with patient chart data from March 2015 to March 2017 at a tertiary care academic hospital in the midwestern United States. In total, 1,069 participants age ≥55 years on an inpatient floor or ICU received a standard 24-hour EEG. The primary outcome was all-cause mortality at 30, 90, 180, and 365 days. Secondary outcomes were time to discharge, and discharge to home.

Having diffuse slowing on standard EEG was significantly associated with 30-, 90-, 180-, and 365-day mortality compared with patients who had normal EEG findings, after controlling for age, sex, and Charlson Comorbidity Index score. When controlling for these factors, patients with diffuse slowing had a significant longer time to discharge and were significantly less likely to discharge to home. Our findings showed that a standard EEG finding of diffuse slowing for inpatients age ≥55 years is associated with poor outcomes, including greater mortality.

This study suggested that the finding of diffuse slowing on EEG may be an important clinical marker for predicting mortality in geriatric inpatients.