Let them sleep: The effects of a scheduled nap during the night shift on sleepiness and cognition in hospital nurses

Aims: The aim of this study was to examine the effectiveness of a scheduled 30-min nap and its interaction with individual factors on sleepiness and cognition during an 8-hr night shift. Design: This prospective, within-subjects study conducted between 2011–2014 compared sleepiness and cognition with/without a nap during the night shift, in 109 female nurses, tested on two nights with and two nights without a nap in counterbalanced order. Methods: Nurses completed the Munich ChronoType Questionnaire for Shiftwork, Pittsburgh Sleep Quality Index and Pre-Sleep Arousal Scale at study onset. They reported sleepiness hourly and performed the Digit Symbol Substitution and the Letter Cancellation Tasks at 3:00 and 7:00 a.m. They took a nap at 4:00 a.m. on nap nights and worked as usual on no-nap nights. Sleep–wake patterns were monitored using actigraphs 24 hr before and during the shift. Caffeine consumption, workload and adverse events were reported. To assess the effectiveness of a scheduled nap, mixed-models and repeated measures analyses of variance were used. Results: Lower levels of sleepiness were found at 5:00, 6:00 and 7:00 a.m. on nap versus no-nap nights. Increments in performance between 3:00–7:00 a.m. were significantly greater on nap versus no-nap nights for Digit Symbol Substitution Task correct responses and Letter Cancellation Task capacity. No interactions between the nap and any of the individual factors emerged. Conclusion: A scheduled nap provides an effective countermeasure against the negative consequences of night-time shift work in female nurses above and beyond interpersonal differences. Impact: Changes in attitude and policy are required to implement this beneficial and cost-effective strategy. Trial registration number: ACTRN12618001857291.