Some workers in Norway's North Sea Oil industry alternate between night and day shifts, the so-called swing shift. A recent study conducted by Postdoctoral fellow Siri Waage and colleagues at the University of Bergen's (UiB) Department of Global Public Health and Primary Care, shows that sleep quality and complaints of insomnia became worse during the offshore work period amongst both these swing shift workers and those who only do day shifts.
The study indicates that it isn't only the shift system itself, but rather long working days over a two-week period in the North Sea that affect sleep, says Siri Waage.
During a typical 14-day work period in the North Sea, the workers will work twelve hours a day whether doing night or day shift.
Although offshore work influences the sleep pattern, there were no differences in subjective health complaints between the groups at the end of a work period than at the beginning, she says.
Around 200 roughnecks participated in Waage's study, which was recently published in the journal Industrial Health.
Even though there were minor variations between the groups, both groups of workers experienced poorer sleep quality and more complaints of insomnia at the end of a two-week work period offshore than they did at the beginning of the work period.
Waage wrote her doctoral thesis Shift work, sleep and health in the petroleum offshore industry at UiB in 2011. The aim of the thesis was to examine the relations between shift work, sleep and health amongst shift workers in Norway's offshore industry.
While the relationship between shift work and adverse health has been well documented, there was until recently quite limited knowledge of the health impacts of offshore work.
Waage's thesis showed that 23 per cent of North Sea workers suffer from so-called shift work disorder (SWD), a circadian rhythm sleep disorder characterised by insomnia and excessive sleepiness affecting people whose work hours overlap with the typical sleep period.
In her thesis conclusion, Waage found that although many offshore workers suffered from SWD, many workers in Norway's petroleum industry seem to tolerate shift work well.