Nurses participating in shift work, especially those working rotating shifts（轮流换班） , face a significantly increased risk of developing Irritable¹ Bowel² Syndrome³ (IBS肠易激综合症) and abdominal⁴ pain（腹痛） compared to those working a standard day-time schedule, according to research published in the American Journal of Gastroenterology（胃肠病学）. "We know that people participating in shift work often complain of gastrointestinal symptoms such as abdominal pain, constipation（便秘） and diarrhea（腹泻） ," says Sandra Hoogerwerf, M.D., assistant professor of internal medicine at the University of Michigan Medical School. "These are the same symptoms of IBS."

IBS is the most common functional⁵ bowel disorder⁶ and is difficult to identify because it is diagnosed by clinical symptoms rather than tests, says Hoogerwerf, lead author of the study. IBS symptoms include recurrent（周期性的，复发的） episodes of abdominal pain or cramping⁷ in connection with altered bowel habits.

Hoogerwerf and her collegues evaluated nurses classified into three groups—214 working permanent day shifts, 110 working permanent night shifts and 75 working rotating shifts between day and night—based on self-reported abdominal symptoms and sleep quality. More than 85% were women.

"Our findings suggest that nurses participating in shift work, particularly those who participate in rotating shift work, have a higher prevalence（流行，普遍） of IBS and abdominal pain. This association is independent of sleep quality," the authors write.

"We know the colon⁸（结肠） has its own biological clock and that's what increases the likelihood of having a bowel movement（排便） in the first six hours of the day," Hoogerwerf says.

"Shift work can cause chronic⁹ disruption of that biological rhythm, resulting in that clock to constantly be thrown off（摆脱，关闭） and needing to adjust, creating symptoms of diarrhea, boating, constipation and abdominal pain and discomfort¹⁰."

The researchers say their study suggests that sleep disturbances¹¹ do not completely explain the existence of IBS or abdominal pain associated with shift work.

"The question now for further research is if IBS and abdominal pain is an underlying¹² manifestation¹³（显示，表现） of a circadian rhythm（昼夜节律，生理节律） disorder," Hoogerwerf says.

Meanwhile, the researchers suggest "practicing gastroenterologists should be aware of this association and educate patients with IBS on the possible impact of their work schedule on their symptoms."