: An impaired level of consciousness is common in elderly patients treated in the emergency department. However, the rate of occurrence of nonconvulsive status epilepticus (NCSE) is not yet known.

Objective: To evaluate the occurrence of NCSE in patients aged ≥ 60 years who presented with a decreased level of consciousness in the emergency department of a general hospital. The study also compared the clinical and EEG findings and 30-day mortality rates between patients diagnosed with NCSE and those with other diagnoses.

Methods: During the year 2023, patients aged ≥ 60 with a consciousness impairment who were admitted to the emergency department of the PUC-Campinas hospital and submitted to EEG at admission were consecutively included. According to the clinical-EEG aspects, the cases were classified into the NCSE and "other diagnoses" groups. Clinical variables and the 30-day mortality rate were compared between the groups.

Results: Of 124 elderly included (mean age 73.9 ± 8.0 years; 64 females), the diagnosis of NCSE was made in 31 (25 %) cases and of "other diagnoses" in 93 (75 %) cases. There was no difference between the groups in age, gender, history of epilepsy, etiology (acute vs. non-acute), and the characteristics of the initial clinical manifestation. In the EEG, there was a high occurrence of delta or theta rhythm and epileptiform discharges (EDs) in the NCSE group. Within 30 days, 46 (37 %) patients died. Mortality was higher in the NCSE group [T test; 20 (64.5 %) vs. 26 (27.9 %); p < 0.001], in cases with acute etiology, with EDs on the EEG, and when the clinical presentation was coma.

Conclusions: NCSE occurred in 25% of the elderly with impaired consciousness who were treated in the emergency department of a general hospital. Unlike the clinical manifestations, the EEG findings differed between elderly patients with NCSE and those with other diagnoses. The mortality rate was high, and there was a higher occurrence in the NCSE.