Doctors are less likely to spot colon polyps in people who get a colonoscopy late in the day compared to those who are first in line, according to a new study.

The findings support previous work and are likely due to doctors' fatigue, researchers say.

"Here we have a repetitive procedure that can lull you into complacency over a long work shift," said Dr. Brennan Spiegel, a professor of medicine at the University of California, Los Angeles, who was not involved in this study.

"Why should endoscopists be immune to the same effects that are known to occur in ... other professions?" such as truck drivers and pilots, he added.

Polyps are abnormal growths that can sometimes develop into colon cancer. During colonoscopy, doctors look for them by inserting a tiny camera into the rectum. The camera is attached to a tube that can also be used to remove polyps before they turn cancerous.

The researchers measured the number of polyps detected over a four-month period among 28 colonoscopy doctors, also called endoscopists. They looked at these results over the course of the day, and noted the patients' position in line.

In total, doctors found at least one polyp in 42 percent of the nearly 1,100 colonoscopies.
For each hour that lapsed throughout the day, there was a four percent reduction in the number of polyps the doctors spotted.

According to the authors of the new report, the highest number of colonoscopies done by one doctor in a day was 12. On average, the twelfth procedure of the day would spot just more than half the polyps detected during the first procedure, the researchers say.

Similarly, each procedure further down in the schedule for that day was linked to about a five percent reduction in polyp detection.

The results "may mean we should move toward shifts, rather than full day schedules," said Dr. Prakash Gyawali of Washington University School of Medicine in St. Louis, who led the work.

"Smaller lesions are being overlooked because of the repetitiveness of the procedure that's making (doctors) less attentive toward the second half of the day," Gyawali told Reuters Health, adding that this is just speculation.

In addition, doctors could be rushing to catch up as their day goes on, for instance, causing them to pass over evidence of polyps.

Still, the number of procedures preceding a patient's colonoscopy on a particular day has a much smaller effect on the likelihood of a doctor catching a polyp than what the patient does to prepare for the colonoscopy, Gyawali said.

That includes properly cleansing the bowels before the exam.

Spiegel said patients should be more concerned with the quality of the doctor, than their position in line at the doctor's office.

Find a doctor who says, "'I'm aware of these studies, and this is what we're doing to compensate,'" Spiegel told Reuters Health.

The U.S. Preventive Services Task Force, a federally supported expert panel, recommends screening for colon cancer in people ages 50 to 75.

But the panel doesn't specify which of the currently available tests—including fecal occult blood testing, sigmoidoscopy, and colonoscopy—should be used.