Shiftwork may lead to GI upset, sick days

Irritable bowel affected by body clock

Rotating shifts have been associated with some serious health effects, including cancer, excessive fatigue, depression, and obesity. A recent study links another disorder to the disruption of changing schedules: irritable bowel syndrome (IBS).

Nurses at the University of Michigan Health System in Ann Arbor who worked rotating shifts were more likely to report symptoms of irritable bowel syndrome — abdominal pain and diarrhea or constipation that lasted at least 12 consecutive weeks. Those symptoms also were more common among nurses working a regular night shift, although the differences didn't reach statistical significance.1

The research indicates the impact that rotating shifts have on the body's circadian rhythm — and the resulting health impacts, says lead author Sandra Hoogerwerf, MD, assistant professor of internal medicine at the University of Michigan Medical School.

"The colon has basically its own clock. If those clock genes somehow don't work the way they're supposed to work, then everything becomes arrythymic," she says. "Any work schedule that disrupts your regular rhythm is probably more likely to be associated with irritable bowel syndrome."

Changing from a day to night schedule is essentially like a bodily jet lag, says Hoogerwerf. It affects not just the sleeping and waking cycle, but other bodily functions, she says.

In the study, researchers surveyed 399 nurses — 214 day shift, 110 night shift, and 75 rotating shift. They completed questionnaires related to bowel symptoms, an irritable bowel syndrome quality of life measure, and sleep disorders. Irritable bowel syndrome was defined as "recurrent abdominal pain or discomfort at least three days per month in the last three months associated with two or more of the following: Improvement with defecation, onset associated with a change in frequency of stool or onset associated with a change in form (appearance) of stool. Irritable bowel syndrome was measured using the Rome III criteria from the Rome Foundation, a McLean, VA-based organization that supports gastrointestinal research.

Almost half (48%) of the rotating shift nurses reported IBS symptoms, compared to 31% of day shift workers. Most of the rotating shift workers (81%) reported having abdominal pain, compared to 54% of day shift workers. The differences were not associated with sleep quality, the researchers found.

The study didn't find that the IBS symptoms created a significant impact on the quality of life of nurses on rotating shifts. But Hoogerwerf notes that IBS is "associated with a substantial economic burden, in that people take time off because of their symptoms and seek medical care."

It's best to avoid rotating shifts, advises Hoogerwerf. People who consistently work night shifts have fewer health impacts, she says. Meanwhile, employees with rotating shifts can use some strategies common to travelers who try to avoid jet lag, she says. For example, the timing of meals may be important or you could gradually eat meals later in the day to adjust to the late-night meal of the shift work.

Melatonin may help readjust the circadian clock and may reduce symptoms such as abdominal pain, she says.

While caffeine may temporarily improve alertness, it isn't an effective tool in resetting the body's clock, says Hoogerwerf. "The problem with caffeine generally is that it has a very mild effect on the central clock, but it's very short lived," she says. "It works for one or two hours, but then you're back to where you were. Caffeine is not a long-term solution. It is a quick fix."


  1. Nojkov B, Rubenstein JH, Chey WD, et al. The impact of rotating shift work on the prevalence of Irritable Bowel Syndrome in nurses Am J Gastroenterol 2010; 105:842–847. (Advanced online publication, February 16, 2010; doi:10.1038/ajg.2010.48.)