Shift work disrupts the body’s circadian rhythm causing not only fatigue but, according to a new study published online in the BMJ, also an increased risk for vascular events.
Anything that upsets the body’s normal functions is bound to affect health. In addition to upsetting the body’s normal body clock, rotating shift work also causes disruption of work-life balance. What’s more, shift work has been associated with a variety of health problems, such as higher risk for type 2 diabetes and elevated cholesterol and blood pressure. One study from 2008, which involved 38 female night shift workers from Denmark, found that the subjects’ breast cancer was an occupational illness, demonstrating that shift work may also have a link to cancer.
Previous studies that looked into the link between shift work and vascular disease, however, have been controversial mostly because, as the researchers of this new study pointed out, of the widely variable parameters and outdated tools and techniques used. These most recent findings involved analysis of 34 previous studies that looked at the vascular disease risk associated with shift work and which involved 2,011,935 people who were either shift workers and regular daytime workers.
For the study, shift working was defined by the research team, led by Daniel G. Hackam, associate professor in the Department of Epidemiology and Biostatistics at Canada’s Western University, as any work schedule that departed from the regular daytime shift of 9am to 5pm, including mixed schedules, rotating shifts, evening shifts, night shifts, and irregular or unspecified shifts.
The study results revealed that: 17,357 participants had experienced a coronary event; 6,598 suffered from heart attacks; and 1,854 suffered from ischemic strokes. The numbers were consistently higher among shift workers than with regular daytime workers. The researchers reported that shift work increased the risk for coronary events by 24 percent, for heart attack by 23 percent, and for stroke by 5 percent; furthermore, there is a 41 percent increased risk for coronary events for night shift workers. The researchers, however, also noted that shift work did not increase risk of death from any cause.
Their analysis also revealed that the 34 studies lacked consistency in definitions, assumptions, sampling criteria, and research methods possibly because smoking habits and socioeconomic status were not taken into consideration.
While the numbers they came up with are relatively modest, the researchers point out that the high number of shift workers in the general population makes these results significant, especially with regards to public health policies and occupational medicine.
The research team recommends educating shift workers about screening programs for health risk factors as well as early signs of problems that have been associated with shift work. The researchers also propose additional studies to identify which groups of shift workers may be more at risk and the better understand the impact of shift work to overall vascular health.