Increased Mortality in Patients with Standard EEG Findings of “Diffuse Slowing”

Abstract

Background/Objectives: We aim to confirm the association between the high risk score on bispectral electroencephalogram (BSEEG) and mortality by comparing outcomes for those with “diffuse slowing” and normal findings on standard EEG. Design: This is a retrospective study conducted with patient chart data from March 2015 to March 2017. Setting: Single center study at a tertiary care academic hospital in the Midwest region of the USA. Participants: 1069 subjects aged 55 years and older who were on an inpatient floor or intensive care unit and received a standard 24-hour EEG. Measurements: Primary outcome was all-cause mortality at 30-, 90-, 180-, and 365- days. Secondary outcomes were time-to-discharge, and discharge to home. Results: Patients with “diffuse slowing” on standard EEG was significantly associated with 30-, 90-, 180-, and 365-day mortality (P < .001) compared to those with normal EEG findings when controlling for age, sex, and Carlson Comorbidity Index. Those with diffuse slowing also had a longer time to discharge (P < 0.001) and were less likely to discharge to home (P < 0.001) when controlling for the same factors. Findings were similar when limiting the study to only patients whose clinical status indicated “awake” at time of EEG, except for 30-day mortality. Conclusion: Our findings show that a standard EEG finding of “diffuse slowing” for inpatients 55 year or older is associated with greater mortality. This study strengthens the importance of the association found between high BSEEG score and mortality.