A study published online Jan. 6 in the American Journal of Preventive Medicine found that women working the night shift was associated with a modest increase of cardiovascular disease mortality, all-cause mortality and lung cancer mortality.
An international team of researchers reviewed data from 74,862 registered nurses in the Nurses Health Study. Mortality from all causes appeared to be 11% higher for women in the 6-to-14-year group, as well as women with 15 or more years of rotating night shift work. CVD mortality appeared to be 19% and 23% higher for those groups, respectively. 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 (25% higher risk).
These results add to prior evidence of a potentially detrimental effect of rotating night shift work on health and longevity, according to a news release. Sleep and the circadian system play an important role in cardiovascular health and antitumor activity, and there is substantial biological evidence that night shift work enhances the development of cancer and CVD, and contributes to higher mortality.
The NHS, which is based at Brigham and Womens Hospital, began in 1976, with 121,700 U.S. female nurses ages 30-55, who have been followed up with biennial questionnaires. Night shift information was collected in 1988, at which time 85,197 nurses responded. After excluding women with pre-existing CVD or other than non-melanoma skin cancer, 74,862 women were included in this analysis.
Rotating shift work is defined as working at least three nights per month in addition to days or evenings in that month. The study is one of the largest prospective cohort studies worldwide with a high proportion of rotating night shift workers and long follow-up time, Eva S. Schernhammer, MD, DrPH, associate professor of medicine, Harvard Medical School, and associate epidemiologist, department of medicine, Brigham and Womens Hospital, Boston, said in the release. A single occupation (nursing) provides more internal validity than a range of different occupational groups, where the association between shift work and disease outcomes could be confounded by occupational differences.
Comparing this work with previous studies, she 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 (e.g., chronotype) warrant further exploration.
Read the study: http://www.ajpmonline.org/article/S0749-3797%2814%2900623-0/abstract