Effects of 90 Min Napping on Fatigue and Associated Environmental Factors among Nurses Working Long Night Shifts: A Longitudinal Observational Study

Abstract

For nurses working long night shifts, it is imperative that they have the ability to take naps to reduce fatigue, and that an appropriate environment is prepared where such naps can be taken. We verified the effects of 90 min napping on fatigue and the associated factors among nurses working 16-h night shifts. We investigated 196-night shifts among 49 nurses for one month. Wearable devices, data logging devices, and questionnaires were used to assess nap parameters, fatigue, and environmental factors such as the napping environment, ways of spending breaks, and working environment. Nurses who nap at least 90 min on most night shifts had more nursing experience. Multivariable logistic regression analysis showed that the environmental factors significantly associated with total nap duration (TND) ≥ 90 min were noise, time spent on electronic devices such as cellphones and tablets during breaks, and nap break duration. The night shifts with TND ≥ 90 min showed lower drowsiness after nap breaks and less fatigue at the end of night shift compared to those with TND < 90 min. Nurses and nursing managers should recognize the importance of napping and make adjustments to nap for at least 90 min during long night shifts.

Keywords: environment; fatigue; long working hours; nap; nurses; shift work; sleep hygiene.

Figure 1

The distribution of total nap duration for each nurse’s during four night shifts. Notes. The vertical axis indicates total nap duration. The horizontal axis indicates the nurses’ ID. The auxiliary line show that the total nap duration is 90 min. Nurses were classified into five groups according to the number of times they were able to take a nap of at least 90 min during their four night shifts. Red crosses: None group (n = 19), Purple pluses: One night shift group (n = 13), Green squares: Two night shifts group (n = 10), Orange Triangles: Three night shifts group (n = 2), Blue circles: Four night shifts group (n = 5), respectively. Abbreviations. ID, identification.

Figure 2

Comparison of change in feelings of fatigue between night shifts with TND ≥ 90 min (n = 59) and TND < 90 min (n = 137) groups. Notes. The sample units in this figure are the number of night shifts. The vertical axis indicates the least squares means in feelings of fatigue (Jikaku-sho shirabe), with higher scores showing higher fatigue. The horizontal axis indicates the measurement points. The blue line is TND ≥ 90 min group, while the red line is TND < 90 min group. Error bars represent 95% confidence interval. (A): total score, (B): drowsiness, (C): instability, (D): uneasiness, (E): local pain or dullness, (F): eyestrain, respectively. The least squares means were analyzed using the mixed linear model, while post hoc t-tests were conducted using their estimates to compare between groups each measurement point. Abbreviations. TND, total nap duration. * p < 0.05.