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