Subjective and objective sleep and sleepiness among tunnel workers in an extreme and isolated environment: 10-h shifts, 21-day working period, at 78 degrees north.

OBJECTIVES: The aim of this study was to examine the effects of extended work hours (10 h on, 14 h off for 21 days) on sleep and sleepiness in an extreme and isolated environment in the far north (Spitsbergen, 78 degrees north). We wanted to examine whether sleep duration, sleepiness and other parameters changed over the 3-week working period and whether the parameters differed between day and night shifts. METHODS: The work consisted of tunnel construction in Svea, Spitsbergen. The participants worked alternate fixed day shift (06:00-16:00) or fixed night shift (18:00-04:00) for a 21-day work period in a counterbalanced, crossover design. The participants were 25 male workers (age 24-60 years). We used subjective and objective measures of sleep (diary and actigraphy) and a subjective daytime sleepiness and function questionnaire. RESULTS: The workers had a high sleep efficiency measured both subjectively and objectively. This did not change across days or between day and night shifts. Total sleep time was significantly shorter (about (1/2) to 1h) during the day shift period than during the night shift period, as measured both subjectively and objectively, but did not differ across days. Subjective ratings of sleepiness did not differ between shifts. CONCLUSIONS: There were few differences between the day and night shift periods and across the 21-day working period, as measured both subjectively and objectively. The subjects experienced few problems and seemed to adapt easily to their work schedule. This contrasts with what is usually the case in more conventional shift work situations, where workers do not adapt well, as measured by sleepiness and various sleep parameters.

Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work.

OBJECTIVES: This study evaluated the effects of bright light and melatonin on adaptation to night work on an oil rig in the North Sea. METHODS: Seventeen persons working a schedule of 2 weeks on a 12-hour shift, with the first week on night shift and the second week on day shift (ie, the swing shift schedule) participated. In a randomized controlled crossover design, the shift workers received a placebo, melatonin (3 mg, 1 hour before bedtime), or bright light (30-minute exposure, individually scheduled) during the first 4 days on the night shift and during the first 4 days on the day shift. Subjective and objective measures of sleepiness (Karolinska Sleepiness Scale and a simple serial reaction-time test) and sleep (diary and actigraphy) were recorded. RESULTS: Subjective measures indicated that melatonin modestly reduced sleepiness at work during the day shift and increased sleep by 15-20 minutes per day. Bright light gave values in between those of melatonin and the placebo, but with few significant results. According to the objective measures, bright light improved sleep to a minor degree during the night shift. Hardly any side-effects were reported. CONCLUSIONS: Melatonin and bright light modestly improved sleep and sleepiness in this field study. In well-controlled simulated nightwork studies, both melatonin and bright light are more effective in alleviating sleepiness and sleep problems. The less effect in this field study may be due to competing or conflicting factors present in real life or to an inoptimal timing and duration of the treatments.

Subjective and objective measures of adaptation and readaptation to night work on an oil rig in the North Sea.

STUDY OBJECTIVES: To study the adaptation and readaptation processes to 1 week of night work (6:30 PM to 6:30 AM) followed by 1 week of day work (6:30 AM to 6:30 PM). DESIGN: Part of a randomized, placebo-controlled, crossover field study. Here, data from the placebo arm are presented. SETTING: Oil rig in the North Sea. Work schedule: 2 weeks on a 12-hour shift, with the first week on the night shift and the second week on the day shift. PARTICIPANTS: Subjects complaining about problems with adjusting to shift work. Seventeen workers completed the study. INTERVENTIONS: N/A. MEASUREMENTS: Subjective and objective measures of sleepiness (Karolinska Sleepiness Scale and simple serial reaction time test) and sleep (diary and actigraphy). RESULTS: Both subjective and objective measures improved gradually during night work. The return to day work after 1 week on the night shift led to a clear increase in subjective sleepiness and worsening of sleep parameters. During the week on the day shift, sleepiness and sleep gradually improved, similar to the improvement seen during night work. The workers indicated that the day shift was worse than the night shift on some of the measures, e.g., sleep length was significantly longer during the night-shift period. CONCLUSIONS: This is one of few studies showing how shift workers in a real-life setting adjust to night work. Both subjective and objective sleepiness and subjective sleep improved across days. The effects were especially pronounced for the subjective data.