Heart disease and cancer risk is higher when working in rotating night shifts, the research has found. Shift workers commonly undergo circadian misalignment, which is the disruption of a person’s natural body clock typically governed by daylight and darkness cycles. Shift work calls for individuals to be awake during times when the body is intended to sleep, and it has been associated with hypertension, inflammation, and cardiovascular disease.
New findings published in the Proceedings of the National Academy of Sciences helped to explain how shift work contributes to cardiovascular disease. The researchers found that short-term circadian misalignment, which occurs during shift work, increases an employee’s risk of cardiovascular disease and inflammatory consequences.
Senior author Frank A. J. L. Scheer said, “We were able to determine, under highly controlled laboratory conditions, the independent impact of circadian misalignment on cardiovascular disease risk factors – blood pressure and inflammatory markers. Our findings provide evidence for circadian misalignment as an underlying mechanism to explain why shift work is a risk factor for elevated blood pressure, hypertension, inflammation and cardiovascular disease.”
The researchers measured blood pressure and inflammatory markers and compared circadian misalignment with circadian alignment in 14 healthy subjects over the course of eight days in a sleep laboratory. One stay included circadian misalignment and the other maintained circadian alignment. Controlling for other contributing factors, such as work stressors, dietary habits, physical activity, as well as family, financial, genetic, health, and social factors, researchers found that circadian misalignment:
- Increased 24-hour systolic blood pressure (SBP) and diastolic blood pressure (DBP)
- Reduced blood pressure dipping, usually associated with sleep
- Decreased measures of autonomic nervous system activity (controlling bodily functions such as blood pressure)
- Increased inflammatory markers
First author Christopher J. Morris concluded, “Our study evaluated “short-term” circadian misalignment in healthy adults. The effect of circadian misalignments on cardiovascular function and inflammatory markers may be different in people with hypertension, and in shift workers. Further research is needed to investigate countermeasures for the adverse cardiovascular effects of circadian misalignment, such as the timing of eating and exercise.”
Night shift work linked to increased risk of cancer and heart disease
Night shift work has also been linked to an increased risk of cancer and heart disease, as found by previous studies. In 2007, the World Health Organization deemed night shift works a possible carcinogen due to its effects on the body’s circadian clock. The findings were published in the American Journal of Preventative Medicine.
The researchers of the study found that women who worked rotating shifts for five or more years had a modest increase in all-cause cardiovascular disease mortality, and those who worked rotating shifts for over 15 years had a modest increase in lung cancer mortality.
The researchers looked at data from nearly 75,000 registered U.S. nurses and analyzed 22 years of follow-up, which led them to their findings. All-cause mortality appeared to be 11 percent higher for women with six to 14 or 15 years or more years of shift work. Cardiovascular disease mortality was 19 and 23 percent higher for those groups as well. Only lung cancer risk was seen to be higher for those who worked shifts for over 15 years, but no other cancer risk was seen.
Eva S. Schernhammer, currently Associate Professor of Medicine, Harvard Medical School and Associate Epidemiologist, Department of Medicine, Brigham and Women’s Hospital, explained that this study, “is one of the largest prospective cohort studies worldwide with a high proportion of rotating night shift workers and long follow-up time. 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.”
She concluded, “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.”
Tips for managing your health in shift work
In order to reduce your risk of cardiovascular disease and other complications associated with shift work, follow some of these tips to help improve health outcomes.
- Minimize working continuous shifts during the night.
- Stick with a set shift work schedule.
- Get enough rest.
- Ensure your environment promotes sleep.
- Avoid caffeine and other stimulants prior to your scheduled sleep time.
- Stick to a scheduled sleep time.
- Bring healthy snacks during your shift work as they are easier to digest at night and are much better for you overall.