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

Abstract 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.