Women who work rotating night shifts for five or more years could be at increased risk of dying from heart disease, researchers warn today.
The risk of lung cancer also appears to increase slightly among women who have worked on a rotating night shift for 15 years and more, according to the study.
In one of the largest global prospective cohort studies with a high proportion of rotating night shift workers and long follow-up time, researchers investigated the possible links between the work pattern and all-cause, heart disease and cancer mortality of almost 75,000 registered nurses in the USA.
Writing in the latest edition of the American Journal of Preventive Medicine, researchers used data from the Nurses’ Health Study and analysed 22 years of follow-up.
They found that working rotating night shifts – working at least 3 nights per month in addition to days or evenings in that month – for more than 5 years was associated with an 11% increase in all-cause mortality.
Heart disease mortality was found to be 19% higher for those who worked the rotating shift for 5 years and 23% higher for those who worked the rotating shift pattern for 15 years.
There was no association between rotating shift work and any cancer mortality, except for lung cancer in those who worked shift work for 15 or more years when a 25% higher risk was recorded.
The Nurses’ Health Study began to collect night shift information in 1988, at which time 85,197 nurses responded.
Dr Eva Schernhammer, associate professor of medicine, Harvard Medical School, said: “These results add to prior evidence of a potentially detrimental relation of rotating night shift work and health and longevity.
“To derive practical implications for shift workers and their health, the role of duration and intensity of rotating night shift work and the interplay of shift schedules with individual traits warrant further exploration.”
Gu F, Han J et al. Total and Cause-Specific Mortality of U.S. Nurses Working Rotating Night Shifts. American Journal of Preventive Medicine. Online ahead of Volume 48, Issue 3 (March 2015). [abstract]
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