The Adenoma Detection Rate (ADR) is a key quality indicator in colonoscopy and is strongly associated with the prevention of interval colorectal cancer (1, 2, 3). In this study, we evaluated double-shift endoscopists, defined as attending physicians performing colonoscopies continuously during both the morning and afternoon sessions on the same day. 

The primary aim was to determine whether fatigue accumulated over a continuous working day affects older endoscopists (≥40 years) more than younger ones (<40 years). Specifically, we sought to compare ADR between morning and afternoon procedures within each age group to identify whether older clinicians show a greater decline in detection performance as the day progresses.

A retrospective study was conducted using colonoscopies performed during the year 2021, a period in which COVID-19–related backlogs led to an increased need for double-shift endoscopists. Only colonoscopies performed by attending physicians who worked continuously during both morning and afternoon sessions on the same day were included, ensuring within-endoscopist comparison and minimizing inter-operator variability.

Exclusion criteria were:

- Inadequate bowel preparation (Boston <2 in any segment)

- Incomplete examinations

- Procedures performed on hospitalized or urgent/emergency patients

- Colonoscopies belonging to the organized colorectal cancer screening program

- Colonoscopies performed by a resident physician.

After applying these criteria, 307 colonoscopies remained for analysis performed by 18 endoscopists (7 younger than 40 and 11 aged 40 years or older). Adenoma Detection Rate (ADR) was compared between morning and afternoon procedures separately for younger (<40 years) and older (≥40 years) endoscopists using contingency tables and chi-square testing, with statistical significance set at p < 0.05.

A total of 161 procedures were performed by younger clinicians. ADR remained stable throughout the day. Morning ADR was 38.6% (27/70) whereas afternoon ADR was 39.6% (36/91). No significant difference was observed (p=1.0), indicating preserved performance across shifts. 

Among 146 procedures performed by older clinicians, ADR varied markedly by time of day, morning ADR was 44.4% (24/54) while afternoon ADR was 23.9% (22/92). This twofold decrease in the afternoon was statistically significant (p=0.0167) suggesting greater susceptibility to within day performance decline.

The effect of procedure timing on adenoma detection appears to be age-dependent. Younger endoscopists maintained consistent ADR throughout the day, with similar performance in morning and afternoon sessions. In contrast, older endoscopists showed a significant decline in ADR during afternoon procedures, with markedly higher detection rates in the morning. Notably, older endoscopists achieved a higher ADR than younger endoscopists during morning sessions, suggesting that their peak performance occurs earlier in the day. Because only within-endoscopist double-shift days were analyzed, these results are unlikely to be confounded by differences in operator skill or technique. These findings highlight the potential value of age-informed scheduling and underscore the need for strategies aimed at mitigating afternoon performance decline in older clinicians.