Reduced rapid eye movement sleep latency in patients with Parkinson's disease.

Rapid eye movement (REM) sleep latency (time from sleep onset to the first REM episode) was measured in 39 patients with idiopathic Parkinson's disease. Reduced REM sleep latency (less than or equal to 65.0 min) was found in a high proportion of patients (69%). Since reduced REM sleep latency may be a trait-like abnormality relatively specific to primary depression, we evaluated this parameter in two groups of parkinsonian patients: depressed (16 patients) and non-depressed (23 patients). Its incidence was significantly higher in depressed patients with Parkinson's disease.