Why Working The Night Shift Has Major Health Consequences

The 15 million Americans who work the night shift won't hesitate to tell you about the toll their work lives take on their sleep schedules. However, quality shut-eye isn't the only thing at risk when it comes to a shift worker's health -- especially among women working rotating night shifts, according to a new study.

Published in the American Journal of Preventive Medicine, the study found that women who have worked rotating night shifts for five years or more not only experience shorter lifespans in general, but also have an increased risk of dying from cardiovascular disease. Those who have performed rotating shift work for 15 years or more are also more likely to die of lung cancer.

In the study, a team of international researchers monitored approximately 75,000 female registered nurses in the United States for 22 years through Nurses' Health Study data, which included an interview with each nurse every other year. Defining rotating shift work as "working at least three nights per month in addition to days or evenings in that month," the researchers asked the women how many years they had worked in this manner.

Of the women who worked rotating night shifts for more than six years, 11 percent experienced a shortened lifespan. Risk of death by cardiovascular disease jumped by 19 percent for those who worked this way for six to 14 years and by 23 percent for those who did so for 15 years or more. Women who worked rotating night shifts for more than 15 years also experienced a 25 percent higher risk of death due to lung cancer.

Previous research has acknowledged shift work's many links to poor health: The World Health Organization deemed it a carcinogen in 2007 due to its repeated disruption of the body's circadian rhythm, and it has also been associated with an increased risk for heart and brain problems. This study further reveals how important a role circadian rhythms play in cardiovascular health and tumor prevention.

"These results add to prior evidence of a potentially detrimental relation of rotating night shift work and health and longevity," Eva S. Schernhammer, M.D., DrPH, an associate professor of medicine at Harvard Medical School and an associate epidemiologist at Brigham and Women's Hospital, said in a statement. "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."