Differences between morning and afternoon colonoscopies for adenoma detection in female and male patients

Colonoscopies performed in the afternoon (PM) have been shown to have lower adenoma detection rates (ADR) compared to those in the morning (AM). Endoscopist fatigue has been suggested as a possible reason. Colonoscopies tend to be technically more challenging in female patients. Furthermore, women have a lower incidence of adenomas then men. The impact of the timing of colonoscopy based on sex has not been studied. We hypothesized that any decrease in ADR in PM colonoscopies would be more pronounced in female patients when compared to male patients.

We retrospectively reviewed colonoscopies performed for screening or surveillance in our outpatient endoscopy center from January 2008 to December 2011. Complete colonoscopies with a documented cecal intubation were included. All patients with a history of colorectal cancer or colonic resection, inadequate bowel preparation, or incomplete data were excluded.

A total of 2305 patients (1207 female) were included. Overall, ADR was significantly higher in AM than in PM procedures. Multivariate analysis demonstrated that ADR for females was lower in PM than in AM colonoscopies (odds ratio [OR] 0.63, 95% confidence interval [CI] 0.44-0.91, P=0.015). There was a non-significant trend towards a lower ADR for males in PM (OR 0.84, 95% CI 0.62-1.15, P=0.28). Females had a prolonged intubation time and a longer procedure time.

The difference in ADR between AM and PM procedures seems to apply mainly to female patients. No significant change in ADR was noted in male patients in the afternoon.