Early morning colonoscopies detect more polyps than colon cancer screenings done later in the day, and the number of polyps found decreases by the hour as the day progresses, a new study has found.

Removing polyps is believed to reduce the risk of colon cancer by 60% to 90%.

The Study

Researchers from the University of California, Los Angeles, analyzed data on 477 people who had colonoscopies in a one-year span at a Veterans Affairs hospital. Colonoscopies that started at 8:30 a.m. or earlier detected 27% more polyps per patient than colonoscopies performed at a later time, according to the study.

Possible Explanations

The improved rate in the early morning may be due to better bowel preparation the night before, according to the researchers. They also suggested that doctor fatigue might also play a role in declining detection as the day wears on.


"We may find that setting a cap on the duration of endoscopic work shifts or other types of adjustments may be helpful," said Brennan M.R. Spiegel, MD, director of the UCLA/Veterans Affairs Center for Outcomes Research and Education and a coauthor of the study.


Dr. Spiegel emphasized that colonoscopy is an effective way to screen for colon cancer at any time of the day and said that people should not worry about getting early morning procedures. The most important thing was to get one.

"The impact of appointment time for any individual is very, very small," Dr. Spiegel said. "Patients should feel confident that colonoscopy is helpful regardless of time of day and should be more focused on the quality and experience of their doctor rather than on the time of their appointment."

The study was published in Clinical Gastroenterology and Hepatology.

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