Further evidence of abnormal non-rapid-eye-movement sleep in schizophrenia

Very low levels of visually scored stage 4 sleep are found in 40% to 50% of acute and chronic schizophrenics. Stage 4 is a visual estimate of high-amplitude delta (0.5 to 3 Hz) electroencephalographic waves; these waves can now be measured directly and reliably by computer. In this pilot study, we carried out such measurement in the successive non-rapid-eye-movement periods (NREMPs). We also sampled and measured visually sleep spindles by NREMP; spindles constitute a second distinctive feature of the NREM electroencephalogram. In five unmedicated, recently rehospitalized schizophrenic patients we found reduced delta amplitude and abundance (and increased spindle density) in NREMP1 (also called "REM latency") as compared with ambulatory normal controls. NREMP1 was also abnormally short with an average length similar to that reported for major depression. These striking abnormalities of NREM sleep may underlie the abnormal rapid eye movement distributions sometimes found in schizophrenic and depressed patients. Further studies are required to evaluate the relation of these NREM abnormalities to psychopathology (and hence their utility as biological "markers") and to rule out confounding effects of hospitalization or undetected napping.