Alertness and psychomotor performance levels of marine pilots on an irregular work roster

ABSTRACT

Fatigue is recognized as an important safety concern in the transportation industry. In this study, our goal was to investigate how circadian and sleep–wake dependent factors influence St-Lawrence River pilots’ sleep–wake cycle, alertness and psychomotor performance levels at work. A total of 18 male St-Lawrence River ship pilots were recruited to a 16–21-day field study. Pilots’ chronotype, sleepiness and insomnia levels were documented using standardized questionnaires. Their sleep–wake cycle was documented by a sleep–wake log and wrist-worn activity monitoring. Subjective alertness and objective psychomotor performances were assessed ~5×/day for each work and rest day. Ship transits were distributed throughout the 24-h day and lasted on average (± SEM) 5.93 ± 0.67 h. Main sleep periods occurred mainly at night, and objectively lasted 6.04 ± 1.02 h before work days. When going to bed at the end of work days, pilots subjectively reported sleeping 7.64 ± 1.64 h in the prior 24 h. Significant diurnal and wake-dependent effects were observed for subjective alertness and objective psychomotor performance, with minimum levels occurring between 09:00 and 10:00. Thus, despite their irregular work schedule, ship pilots presented, as a group, a diurnal variation of alertness and psychomotor performance indicative of a day-oriented circadian system. Important inter-individual differences were observed on psychomotor performance mesor and phase. In individuals, earlier phases in psychomotor performance were correlated with earlier chronotype. This study indicates that both circadian and homeostatic processes modulate alertness and psychomotor performance levels with worst levels reached when long shifts ended in the morning. This work has potential applications as it indicates fatigue countermeasures considering both processes are scientifically based.

KEYWORDS:

• Marine pilots
• shift work
• circadian rhythms
• sleep–wake cycle
• psychomotor performance
• subjective alertness
• chronotype
• inter-individual differences

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Acknowledgements

The authors thank the pilots, ship owners and operators who agreed to this study. We also thank all of those who contributed directly and indirectly to this study, in particular the members of the Project Follow-up Committee (Sylvia Masson, Joseph-Marie Fraser, Michel Fortin, Martin Foisy, Jean-Marie De Koninck), and the staff of the Centre for Study and Treatment of Circadian Rhythms, Douglas Hospital Research Centre (Stephen Ng and Olivier Boivin for recruitment and data collection, as well as Manon Gagnon and Johanne Gauthier for administrative support).

Declaration of interest

DBB acts as a consultant on shiftwork-related issues. All other authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Additional information

Funding

This research was funded by the Corporation des Pilotes du Saint-Laurent Central Inc. (CPSLC) and the Laurentian Pilotage Authority (LPA).