Night shift more dangerous: study

Canadians who work nights and rotating shifts are almost twice as likely to be injured on the job as those working day shifts, researchers in British Columbia have found.

Their study, published in the Scandinavian Journal of Work, Environment and Health, was based on Statistics Canada data of 30,000 Canadians comparing people working different shifts between 1996 and 2006.

Night-shift work was associated with double the risk of work injury for women and 1.9 times the risk for men, Imelda Wong of the University of British Columbia's School of Environmental Health and her co-authors found.

Similarly, rotating shift work was linked with 2.29 times the risk of work injury for women, based on the analysis of workplace compensation claims.

"I'm hoping that this will increase the awareness that those who work outside regular 9-to-5 hours are at a higher risk of injury than those who work during the day," Wong said.

The researchers concluded "that additional occupational health and safety policies and programs are needed to reduce risk of work injury among night and rotating shift workers, especially among women."

For example, the length of night shifts may need to be shorter than day shifts, and shift workers may need longer breaks to prevent fatigue at work.

Wong said she hopes the findings will encourage a dialogue between workers and their employers to explore options that can help reduce risk on injury at work.

Overall, the risk of work injuries in Canada decreased over the decade, but not for night-shift workers.

Gender split

Because women are more likely to be responsible for childcare and housework, they may have more trouble adjusting to shift work and keeping regular sleep schedules, the researchers suggested.

In time, the fatigue may lead to an increased chance of injury on the job, the study's authors said.

More Canadians are working non-standard hours. An earlier report for Human Resources and Development Canada found a 17 per cent increase in the number of people working outside of "nine to five" from 1991 to 1995, and that women in rotating shift work reported more difficulties in managing work-home conflict.

Among women, the number in rotating and night-shift work increased by 95 per cent during the study period, mainly in the health care sector. For men, the increase was 50 per cent, mostly in manufacturing and trades.

Of the 2.7 million lost-time injury compensation claims awarded in Canada in 2006, the researchers estimated about 107,000 among men and 200,000 among women could be attributed to the higher risk of injury associated with shift work.

The researchers noted several limitations of the study, such as how less than half of workplace injuries are reported and not all are awarded compensation. Also, regular night- and rotating-shift workers may be less likely to file a claim, another source of underestimation.

The study did not look at other aspects of shift work, such as length of shift, that may matter for workplace injuries.

The study was funded in part by WorkSafeBC, the province's workers' compensation board.