Over three years' follow-up, industrial shift workers have greater increases in a measure of arterial stiffness, compared to day workers—which may be an early sign of increased risk of cardiovascular disease (CVD), reports a study in the April Journal of Occupational and Environmental Medicine.
Led by Marit Skogstad, MD, PhD, of the Norwegian Institute of Occupational Health, Oslo, the researchers assessed changes in CVD risk factors over time in two groups of workers at insulation material plants: 57 rotating shift workers and 29 day workers.
In initial blood measurements, shift workers had higher levels of markers of inflammation, such as C-reactive protein. Shift workers also had higher levels of adhesion molecules such as vascular cell adhesion molecule 1, which contribute to the development of atherosclerosis.
At follow-up, the shift workers also had greater increases in pulse wave velocity (PWV)—a measure of arterial stiffness. Over three years, PWV increased by 1.29 meters per second (m/s) in shift workers, compared to 0.11 m/s in day workers. Changes in other CVD risk factors—including blood pressure, cholesterol, inflammatory markers—were similar between groups. The changes did not appear to be related to respirable dust levels in the workplace, which were below Norwegian occupational exposure limits.
Previous findings in a subset of the same group of workers suggested that shorter sleep duration was associated with an increase in blood pressure and possibly PWV. "Thus, sleep restriction might explain our findings of increase in PWV but also in mediators of inflammation," the researchers write.
Shift work is known to be associated with type 2 diabetes, weight gain, and some cancers, but its possible association with CVD has been unclear. Recent reports have suggested that CVD risk increases with number of years of shift work.
The new study provides evidence linking shift work to a faster increase in arterial stiffness, possibly related to decreased sleep and increased inflammation. "These changes might increase the risk for future CVD," Dr. Skogstad and coauthors write. "This warrants a focus on organizing night work compatible with sustained working life."
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About the Journal of Occupational and Environmental Medicine
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) is the official journal of the American College of Occupational and Environmental Medicine. Edited to serve as a guide for physicians, nurses, and researchers, the clinically oriented research articles are an excellent source for new ideas, concepts, techniques, and procedures that can be readily applied in the industrial or commercial employment setting.