Sleep EEG in depressed and nondepressed patients with Parkinson's disease

Sleep patterns of two consecutive nights were analyzed in 26 drug-free patients with Parkinson's disease (PD), who were clinically divided into depressed (n = 8) and nondepressed (n = 18) groups. Sleep electroencephalographic (EEG) recording showed significantly shorter rapid eye movement (REM) latency in depressed PD patients (41.1 +/- 21.7 min) compared to nondepressed PD patients (129.0 +/- 84.9 min, p less than 0.002). Furthermore, shortened REM latency (less than or equal to 65.0 min) was observed with significantly more frequency in depressed PD patients (6 out of 8) compared to nondepressed PD patients (4 out of 18, p less than 0.02). The other sleep parameters studied did not differ significantly between the two groups of patients. Because shortened REM latency is one of the most reliably documented biological features of major depression, these findings may be of some importance for understanding the nature of depression in the course of PD.