An investigation of the effects of different shift schedules on the fatigue and sleepiness of officers on oil tankers during cargo handling operations.

Cargo handling is an operation, which requires a high level of performance from the officer of the watch (OOW). This study aimed to investigate the effect of different shift schedules on sleep quality, cognitive performance, and sleepiness of 139 OOWs on oil tankers with 4on-8off shifts, during the first shift of cargo handling. Sleep quality (Pittsburgh Sleep Quality Index (PSQI)), level of sleepiness (the Karolinska Sleepiness Scale (KSS)), Psychomotor Vigilance Task (PVT), and Arrow Flanker task performance were examined. The results showed that OOWs with (00:00-04:00, 12:00-16:00) and (04:00-08:00, 16:00-20:00) shifts had impaired cognitive performance and higher sleepiness during the cargo handling operation, and they also experienced impaired sleep quality. The results demonstrated that the circadian rhythm and homeostatic sleep drive have a greater impact on cognitive performance and sleepiness than time on shifts. These results suggest that allocating rest hours immediately before the cargo handling operation may reduce the risk of fatigue. Practitioner Summary: To the best of our knowledge, this maritime field study shows for the first time the prevalence of seafarers' sleepiness and cognitive performance while on duty during cargo handling, using a pre-post shift comparison between three different shifts. The results show the negative effects of keeping watch at night on sleep quality, sleepiness, and the impaired cognitive performance both in the day and the night shifts.