Circadian rhythms in deep body temperature,urinary excretion and alertness in nurses on night work

Fourteen volunteer nurses who worked on the night shift at a local hospital recorded their times of sleep, mealtimes and any illness or complaints for 12 consecutive days which included at least one spell of night work and rest days. Whilst awake they made regular assessments of their alertness and collected frequent urine samples for analysis of the rate of excretion of a number of constituents. Rectal temperatures were automatically recorded throughout the day and night. Volunteers were divided into those who worked 1–3 successive nights (short term) and those who worked longer ‘blocks’ (long term). There was no difference between the two groups when their subjective assessment of alertness during night work was considered and in both groups there was a similar change in circadian rhythms when rest days and work days were compared. However, there were differences in the amount of day-time sleep that was taken, the temperatures measured, both on and off duty, between 20.00 and 08.00 hours and the number of complaints recorded. These differences are discussed in terms of the ‘commitment’ of individuals to night work and of the possibility that this will change with family and social factors.