Physicians during and following night call duty--41 hour ambulatory recording of sleep.

Six house officers at two Stockholm hospitals were subjected to 41 h of continuous ambulatory recording of EEG and EOG in connection with night call duty, and to 24 h in connection with normal day work. The results showed that night call duty greatly interfered with sleep, reducing its duration to 4 h. The reduction mainly affected sleep stages 2 and REM. SWS was not affected, whereas EEG spectral power density in the 0.5-7.9 Hz band was suppressed. During subsequent time off, napping and night sleep increased total sleep length above baseline levels. It was concluded that night call duty of the present type causes considerable sleep loss.