title: Morning colonoscopies are associated with improved adenoma detection rates.
abstract: BACKGROUND
  Higher adenoma detection rates are associated with decreased risks for subsequent colorectal cancers. Studies have suggested that adenoma detection rate (ADR) may be affected by timing of colonoscopy due to endoscopist fatigue later in the day. The aim of our study is to assess the influence of the timing variables on ADR.
  
  
  METHODS
  Univariate analysis and multivariate logistic regression analysis were performed on a prospective colonoscopy database, comparing ADR for colonoscopies performed in the morning shift (AM) and in the afternoon shift (PM) over a 1-year period. Each shift lasted 4 h. Only elective outpatient completed colonoscopies with adequate bowel preparation, performed by four certified staff endoscopists, were included. Surveillance colonoscopies for cancers were excluded. ADR was defined as the detection of at least one histologically confirmed polyp during colonoscopy.
  
  
  RESULTS
  A total of 533 colonoscopies were included. ADR was 25 % in the cohort. Mean age was 59 (SD 14.1). Two hundred and seventy (50.6 %) were done in the AM and 263 (49.4 %) were done in the PM. ADR was 29 % in the AM group compared to 21 % in the PM group (p = 0.03). Excluding time needed for polypectomy, the mean time taken for scope withdrawal was significantly longer in the morning group (12 min) compared with the afternoon group (10 min) (p = 0.002). The longer withdrawal time in the morning was significantly associated with increased ADRs (OR 1.104, 95 % CI 1.063-1.147) (p < 0.0001).
  
  
  CONCLUSIONS
  Timing of colonoscopy is an independent predictor for ADR. Colonoscopies performed in the morning have a longer mean withdrawal time, thus leading to a significantly higher ADR. As endoscopists concentration decreases as the day progresses, this may account for the shorter time spent on colonoscopies on the afternoon.
authors.affiliation: Department of General Surgery, Ng Teng Fong General Hospital, Jurong Health Services, 1 Jurong East Street 21, Singapore, 609606, Singapore.
authors.forename: Tze Yeong
authors.initials: TY
authors.lastname: Teng
authors.affiliation: Department of General Surgery, Ng Teng Fong General Hospital, Jurong Health Services, 1 Jurong East Street 21, Singapore, 609606, Singapore.
authors.forename: Shao Nan
authors.initials: SN
authors.lastname: Khor
authors.affiliation: Department of Epidemiology, Ng Teng Fong General Hospital, Jurong Health Services, 1 Jurong East Street 21, Singapore, 609606, Singapore.
authors.forename: Manimegalai
authors.initials: M
authors.lastname: Kailasam
authors.affiliation: Department of General Surgery, Ng Teng Fong General Hospital, Jurong Health Services, 1 Jurong East Street 21, Singapore, 609606, Singapore.
authors.forename: Wei Keat
authors.initials: WK
authors.lastname: Cheah
authors.affiliation: Department of General Surgery, Ng Teng Fong General Hospital, Jurong Health Services, 1 Jurong East Street 21, Singapore, 609606, Singapore. Cheryl_Lau@juronghealth.com.sg.
authors.forename: Cheryl Chien Li
authors.initials: CC
authors.lastname: Lau
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002983:Clinical Competence / Q000706:statistics & numerical data*; D003113:Colonoscopy / Q000592:standards* / Q000706:statistics & numerical data; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging*; D016208:Databases, Factual; D005221:Fatigue; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D013997:Time Factors
keywords: Adenoma detection rate; Colonoscopy; Intubation; Morning and afternoon timing; Quality indicators; Screening; Withdrawal time