[Objective and subjective measures of sleep of shift-working nurses]

To objectively evaluate sleep quality of shift-working nurses, we used an Actiwatch 2, a watch-like actigraphy device designed to measure sleep and wakefulness based on the amount of movement. Subjective sleep quality was also assessed using the St. Mary's Hospital Sleep Questionnaire.

Nineteen shift-working nurses wore the Actiwatch 2 for 5 days. The monitoring began with 2 days of the morning shift, which were followed by a 16-hour night shift and a rest day. Sleep recordings were obtained four times: night sleep after the second morning shift ("sleep 1"), napping on the night shift ("nap 1"), daytime napping after the night shift ("nap 2") and night sleep after the night shift ("sleep 2"). Actiwatch 2 sleep measures include sleep onset latency, snooze time, sleep efficiency, and percent sleep. In addition, the perceived quality of sleep was obtained using five questions of the St. Mary's Hospital Sleep Questionnaire. Objective and subjective sleep quality were compared between different sleep/nap times: sleep 1 vs. sleep 2, and nap 1 vs. nap 2.

Percent sleep of sleep 2 was higher than that of sleep 1. In almost all responses to the St. Mary's Hospital Sleep Questionnaire, the perceived quality of sleep on sleep 2 was better than those of sleep 1, and that of nap 2 was better than nap 1. A significant negative correlation was found between the perceived sleep quality of nap 2 and the characteristics of participants (age, number of children, and length of career). There were positive correlations between the perceived sleep quality of sleep and percent sleep, and between the perceived sleep quality of nap and sleep efficiency. Moreover, the perceived sleep quality of nap 2 tended to decrease in participants whose bedtime deviated from the mean value on morning shift days and the rest day.

We found that perceived sleep quality is related to percent sleep, and that the perceived sleep quality of nap is related to sleep efficiency. The results suggest that improving the sleep quality of daytime napping after the night shift is necessary for nurses with children, and that keeping a regular bedtime is necessary to improve the sleep quality of napping on the night shift.