Introduction Sleep and fatigue problems are among the most common health and safety concerns in the offshore oil and gas industry. To understand sleep and fatigue problems offshore, we examined the course of sleepiness and sleep parameters across 2-2 offshore rotations and compared pre-departure (1 week), offshore work (2 weeks) and recovery (1 week) periods.

Methods A prospective cohort study was conducted among N=60 offshore workers. Sleepiness was measures twice a day (after awakening, after dinner) with the Karolinska Sleepiness Scale. A mean daytime sleepiness score was calculated. Sleep parameters were measured continuously with a wrist-worn actigraph (MotionWatch 8®, Camntech). Measured sleep parameters included: time in bed (TIB), sleep latency (SL) and sleep efficiency percentage (SE%). Changes in sleepiness and sleep parameters during periods were investigated using linear mixed models.

Results Analyses were conducted among N = 49 offshore workers (82%). Mean daytime (F = 5.60; p < 0.01) and evening sleepiness (F = 7.81; p < 0.001) changed significantly during the periods. Both, mean daytime and evening sleepiness were significantly higher during recovery periods compared to pre-departure (Mean_daytime: 1.78, 95% CI [0.73–2.83] p < 0.01; Evening: 2.75, 95% CI: [1.33–4.16] p < 0.001) and offshore work periods (Mean_daytime: 1.25, 95% CI [0.40–2.11] p < 0.01; Evening: 2.17, 95% CI [1.02–3.32] p < 0.001).

Significant changes during the periods were found for TIB (F = 29.39; p < 0.001) and SL (F = 3.03; p < 0.05). TIB was significantly shorter during the offshore work period than during the pre-departure (−28.67, 95% CI [−48.13–−9.22] p < 0.01) and recovery periods (−52.91, 95% CI [−72.77–−33.05] p < 0.001). SL was significantly shorter in the recovery period compared to the offshore work period (1.50, 95% CI [1.07–2.11] p = 0.02). Morning sleepiness and SE% did not change significantly during the periods.

Conclusion Sleepiness and sleep parameters significantly changed during 2-2 offshore rotation periods. These changes should be considered in the management of fatigue, health, safety and performance in offshore operations.