Subjective and objective sleepiness among oil rig workers during three different shift schedules.

OBJECTIVES: Examine sleepiness in three different shift work schedules (within-subject design) in the offshore oil industry. METHODS: Sleepiness was measured in 19 oil rig workers, using subjective (Karolinska Sleepiness Scale; Accumulated Time with Sleepiness) and objective measures (reaction time). The work schedule consisted of two weeks of 12 h day work (day shifts), two weeks of 12 h night work (night shifts), and two weeks of swing shift work (one week of night work followed by one week of day work). RESULTS: Sleepiness was highest during the first days of night and swing shifts, and also in the middle of the swing shift work period, but gradually decreased as the days on the night shift progressed. While at home following the two-week work period, the workers reported more subjective sleepiness after night shift than after day or swing shifts. Reaction time tests during the work period showed no significant differences between the shift schedules. There was a significant shorter reaction time the last day compared to the beginning or middle of the work period. CONCLUSIONS: Subjective sleepiness was higher during the first days of night work compared to day work, and also when the swing shift workers changed from night work to day work in the middle of the two-week work period. Subjective sleepiness was increased at home following night shifts compared to after day and swing shifts, suggesting that swing shift workers adapted their circadian rhythm during their second period of work, during the day shift week, offshore.

Individual differences in tolerance to shift work--a systematic review.

Shift work tolerance is a term describing the ability to adapt to shift work without adverse consequences. In this paper we systematically review literature published investigating the relation between individual differences such as age, gender, personality, morningness/eveningness as well as biological variables and different measures of shift work tolerance from 1998 till 2009. A total of 60 articles were included in this review, of which ten studies were classified as longitudinal, while the rest were classified as cross-sectional. Overall, the studies indicate that young age, male gender, low scores on morningness, high scores on flexibility and low scores on languidity, low scores on neuroticism, high scores on extraversion and internal locus of control and some genetic dispositions are related to higher shift work tolerance. More longitudinal studies, especially concerning personality, are needed to make conclusions about the predictive power of individual differences for shift work tolerance.