New Brigham and Women’s Hospital (BWH) research has found that long-term rotating shift work may increase a woman’s risk of dying from heart disease or lung cancer.
To examine the impact of rotating night shift work on mortality, BWH epidemiologist Dr. Eva Schernhammer and her research team analyzed 22-year medical histories of nearly 75,000 female nurses from the Nurses’ Health Study. The composition of the Nurses’ Health Study – exclusively female nurses – was particularly advantageous for Dr. Schernhammer’s purposes, as many nurses have rotating-shift schedules.
Compared to nurses who never worked night shifts, the researchers found that nurses who regularly worked rotating shifts for 6 to 14 years were 19 percent more likely to die from heart disease. (For this study, a rotating-shift worker was defined as someone who worked at least three nights per month, in addition to shifts at other times of the day.) Women who worked rotating shifts for 15 years or more were 23 percent more likely to die from heart disease and 25 percent more likely to die from lung cancer. The study also found that rotating shift workers were slightly more likely to die sooner, regardless of the cause.
“These results add to prior evidence of a potentially detrimental effect of rotating night shift work on health and longevity,” says Dr. Schernhammer.
Dr. Schernhammer’s findings tie in with prior research from the BWH Division of Sleep and Circadian Rhythm Disorders that examined the health effects of rotating-shift work. Their study demonstrated that a combination of insufficient sleep and sleep patterns that go against the grain of our body’s biological clock (circadian rhythm) – i.e., not regularly sleeping at night – may lead to an increased risk of type 2 diabetes and obesity. Researchers found that when study participants’ sleep, activity, and meal patterns were out of synch with circadian rhythms for three weeks, their resting metabolic rate decreased dramatically – translating into a yearly weight gain of about 10 pounds – and their blood sugar spiked and remained higher for hours after meals – a telltale sign of developing diabetes.
More to Do
The World Health Organization has already gone so far as to classify night work as a probable carcinogen. Dr. Schernhammer, however, stresses that much more work needs to be done to confirm the relationship between night work and health risks and to drill down to the primary cause(s) of these negative outcomes.