An electroencephalographic investigation of late-onset schizophrenia

We performed awake and resting electroencephalograms (EEGs) on 22 subjects with DSM-III-R schizophrenic disorder of late onset (at or after age 50 years), and compared them with the EEGs of 33 healthy community controls matched for age and gender. The EEGs were rated qualitatively and a 2-minute, artifact-free tracing from each subject was quantified manually by an experienced neurophysiologist unaware of the identity of the subject group. The only significant difference was the presence of more generalized slowing in the EEGs of schizophrenia patients, which was at least partially accounted for by the effect of neuroleptic drugs. The schizophrenic subjects did not have a greater prevalence of epileptiform disturbances or abnormal asymmetry of the EEG compared to the control group. Our study does not suggest the presence of underlying dementia in schizophrenia of late onset.