The after-effects of night work on short-term memory performance.

The aim of this study was to assess the after-effects of night work on mental performance. Twenty experienced shift workers were examined in a baseline condition and during recovery after a night shift period. For control purposes eight other workers were studied in a similar baseline condition and during recovery after a non-night shift period. The subjects performed memory search tasks before and after a bicycle ergometer test. Cycling had different effects on mental performance, leaving the speed and accuracy of the reactions unchanged in the baseline and the non-night-recovery condition, while decreasing the mental performance in the night-recovery condition. Also in this condition a higher level mental effort investment was measured. These results suggest an incomplete recovery on the first fully undisturbed day-off (32 h) after a period of night work, manifesting itself in a deterioration of the efficiency of the information processing.