Sleep patterns of offshore day-workers in relation to overtime work and age

• Offshore personnel work extended tours (14 × 12 h shifts) in a stressful environment.
• About half offshore day-workers also work overtime (on average, 16 h/week).
• Overtime workers report impaired sleep relative to those who do no overtime.
• Longer overtime hours predicted less sleep in a linear dose–response pattern.
• During leave weeks, sleep was ∼1 h/day longer than during offshore weeks.

In addition to long contractual hours during offshore weeks (14 × 12 h shifts), many personnel on North Sea oil/gas installations also work overtime, but little is known about the implications of overtime for sleep patterns offshore. In this study, the additive and interactive effects of overtime and age were analysed as predictors of sleep duration and sleep quality among offshore day-workers (N = 551), 54% of whom reported overtime. Sleep duration and quality were impaired among personnel who worked overtime, relative to those who worked only standard shifts; there was also an inverse dose–response relationship between overtime hours and sleep duration. Although the sleep measures were more favourable during shore leave than during offshore weeks, there was little evidence of compensatory sleep patterns. These findings are discussed with reference to known performance and health effects of short sleep hours; formal guidance on overtime work offshore is noted; and methodological issues are considered.