It's been a hard day's night: A diary study on hardiness and reduced sleep quality among naval sailors

A hardy disposition is regarded as an advantage in demanding and stressful environments and is associated with improved military performance. Recent evidence suggests that hardiness may also be related to resilience with respect to sleep disturbances. The aim of the present study is to investigate the moderating role of hardiness in the sleep quality – job performance relationship in a sample of naval cadets during a demanding training exercise. We hypothesize that (1) Hardiness positively influences daily job performance, (2) daily sleep quality positively influences daily job performance, and (3) Hardiness buffers the impact of poor daily sleep quality on daily job performance. A sample of 56 naval cadets first filled in a general questionnaire, and then filled in a daily diary assessing sleep quality during a 30-day training mission across the Atlantic Ocean. Daily job performance was assessed by using peer-ratings. Results of multi-level analyses showed a positive main effect of hardiness on job performance. Hardiness also moderated the sleep quality – job performance relationship. Cadets high (vs. low) on dispositional hardiness were less affected by poor sleep quality, also after controlling for neuroticism. The results suggest that hardiness moderates the effect of poor sleep quality on job performance.

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