A systematic review found little clear evidence to support the amount of time that night shift workers should spend napping. These findings were published in Sleep Medicine Reviews.
Researchers from the University of Pittsburgh searched publication databases for studies of nap duration. Brief naps were defined as 30 minutes, moderate as 31-60 minutes, and long naps as >60 minutes. A total of 7 studies presented in 11 publications were reviewed.
Among the 140 study participants, 52% were night shift workers and 48% healthy volunteers. Only 2 of the studies recruited night shift workers who were employed as air-traffic control specialists and at an oil refinery.
Among studies which assessed performance within an hour of a nap, 2 studies found a brief nap was superior and 2 other studies had mixed results. More than an hour after the nap, 2 studies favored a long nap, 1 a moderate nap, 1 found mixed results, and 1 found no impact of nap duration.
Fatigue or sleepiness within 60 minutes of the nap was found to have no impact (n=2) or mixed results (n=3) on the basis of time and more than 60 minutes after the nap, 1 study favored a moderate nap, and the others found no impact (n=3) or mixed results (n=3).
Health indicators more than 60 minutes after the nap favored a moderate nap in 1 study, 4 others had mixed results, and 1 found no impact.
All 7 studies were at high risk for bias and had low quality of evidence. There was significant variation in timing of naps ranging from 00:00 (midnight) to 04:10. Little consistency was provided to participants in which some were informed about study motivation and others were blinded.
Researchers were unable to assess their population of interest, night shift workers, as only 2 studies recruited from this population.
These data indicated that there was little evidence to guide optimum nap duration for night shift workers in order to optimize performance, safety, fatigue, and health. Additional studies are needed.
Patterson PD, Liszka M K, Mcilvaine QS, et al. Does the evidence support brief (<30 mins), moderate (31-60 mins), or long duration naps (61+ mins) on the night shift? A systematic review. Sleep Med Rev. Published online May 19, 2021. doi:10.1016/j.smrv.2021.101509