O-188 Sleep timing and duration after night shifts among permanent night workers and shift workers

IntroductionNight work may be organized as permanent night work or as part of shift work, which in turn may affect sleep and health. We aimed to compare timing and duration of sleep in relation to permanent night work and shift work.Materials and MethodsSleep was assessed by diaries and actigraphy on up to 26 days among 89 male industry workers with permanent night work and 72 male police officers with shift work. Statistical analyses with adjustment for age were performed taking repeated measures into account. The study was approved by the National Ethical Committee.ResultsPreliminary results show that after a night shift, permanent night workers fell asleep in the morning (between 7:00–9:00) on 78% of the days, whereas this was the case for 95% of days among shift workers. On recovery days (day off or a day shift), this was only observed on 1.6% of days among permanent night workers and 0.6% of days among of shift workers. Instead, on the majority of recovery days (77% for permanent night workers and 92% for shift workers) sleep was initiated between 22:00–2:00, and on some days (21% for permanent night workers and 7% for shift workers) sleep was initiated between 2:00–6:00. Permanent night workers slept on average 5:49 h:mm (standard error of the mean (sem) 0:05 h:mm) after a night shift and 7:41 h (sem 0:08 h:mm) on a recovery day, whereas shift workers slept 5:39 h:mm (sem 0:06 h:mm) and 7:21 h:mm (sem 0:05 h:mm), respectively. Sleep duration differed between days with night shifts (p<0.01) and recovery day and between permanent night workers and shift workers (p<0.01), but there was no interaction effect (p=0.124).ConclusionsOverall, these preliminary results indicate only minor differences between timing and duration of sleep among night shift workers and permanent night workers.