Data was retrospectively collected from an endoscopic database of four referral training hospitals in South Korea. A total of 388 consecutive patients, who were admitted for peptic ulcer bleeding via the emergency room (ER) between January 2007 and December 2009, were enrolled. All subjects had endoscopically confirmed peptic ulcer bleeding.

Patient data were collected from medical records, which were reviewed by endoscopists who were blinded to the aim of this study. The Institutional Review Board of Gangnam Severance Hospital approved this study.

We excluded patients with variceal bleeding, Mallory-Weiss tear, lower gastrointestinal bleeding, or bleeding from malignant ulcers. Peptic ulcers without stigma of recent bleeding (Forrest III[11]) were also excluded due to the obscure source of bleeding.

All four hospitals that participated in this study were referral training centers in urban areas and have formal out-of-hours emergency endoscopy services. In these centers, at least one endoscopist is scheduled to be on duty for emergency calls for endoscopy, regardless of time and day, even on weekends or at night. Endoscopy is generally conducted as soon as possible in patients with suspected UGIB. However, we do not have a night shift; therefore, one of the day shift endoscopists has to be on duty at night when on emergency call. All on-duty endoscopists can handle the available endoscopic hemostatic procedures. All endoscopic hemostatic procedures were performed using the same protocol set by the guidelines of the Korean Society of Gastroenterology[12]. Hemostatic procedures were carried out on Forrest Ia to IIb peptic ulcers[11].

The levels of experience of endoscopists who performed endoscopic hemostasis in UGIB varied slightly among the four centers according to their policies. In one institution, senior instructors were responsible for both daytime and nighttime endoscopic hemostasis, while hospital staff took charge of hemostatic interventions in both daytime and nighttime in the other three institutions. Thus, for a given institution, available expertise remained generally constant day and night.

The weekend group was defined as patients who presented to the ER from Friday midnight to Sunday midnight, and the remaining patients were categorized as the weekday group. The nighttime group was defined as patients who presented to the ER between 18:00 and 8:00 the next day. Endoscopy was classified as “early” if the procedure was performed within 24 h[13]. Active bleeding indicated spurting or oozing, which was based on classification from Ia to Ib according to endoscopic findings[11]. Rebleeding was defined as bleeding within 2 wk that required secondary hemostasis or was associated with hematemesis; melena with overt decrease in hemoglobin over 2 mg/dL; status requiring blood transfusion; shock (systolic blood pressure < 90 mmHg); or endoscopic findings of recent bleeding, such as spurting, oozing, or adherent clot[14,15].

Parameters were chosen only for characteristics representative of bleeding, and were classified into baseline characteristics and treatment outcomes; the following intergroup comparisons were made: weekday vs weekend and daytime vs nighttime. The baseline parameters were age; disease type; endoscopic findings, including Forrest class; Rockall score[16,17]; and Charlson score. The Charlson score is a system for the classification of severity that uses recorded data on a patient’s diagnosis to assign a weight to morbidity, thereby predicting a patient’s risk of death. To calculate the Charlson score, we included age factor in the comorbidity score, which is called the Charlson age comorbidity index (CACI)[18]. As treatment outcome parameters, the primary endpoints were mortality rate, rebleeding, length of stay, and the need for surgery or embolization.

Data was analyzed using the Statistical Package for the Social Sciences (SPSS, 18.0 Inc, Chicago, United States) software with the assistance of the Yonsei University Statistical Consulting Center. Sensitivity and specificity were calculated with 95% confidence intervals and P values less than 0.05 were regarded as significant. According to the 95% confidence interval, we present data as the mean ± SE. The comparison of categorical variables between the two groups was carried out using the χ² test. A logistic regression model was used to analyze the effect of categorical variables and adjust for potential confounders. The comparison of continuous variables between the two groups was carried out by t-test. A linear regression model was used to analyze the effect of continuous variables and adjust for potential confounders.

The weekday group included 326 patients and the weekend group comprised 62 patients. There were no significant intergroup differences in demographics, except for age (Table 1). The mean age of the weekend group was younger than the weekday group by 5 years (60.7 ±0.85 years in the weekday group vs 55.7 ± 2.10 years in the weekend group, P = 0.023). The ages in both groups had normal distributions; the weekday showed skewness and kurtosis values of -0191 and -0.627, respectively, and the skewness and kurtosis values of the weekend group were -0.83 and -0.760, respectively. All outcome analysis was age-adjusted because age is an important confounding factor for treatment outcomes, including mortality. In order to adjust for age, linear regression was used for continuous variables and logistic regression was used for categorical variables. However, there were no significant differences between the two groups in the patterns and sites of bleeding, Rockall scores, Charlson scores, or comorbidities (Table 1).

Endoscopic therapy was performed in patients with Forrest Ia to IIb ulcers, and the following hemostatic tools were frequently used: argon plasma coagulation, hemoclipping, and epinephrine injection as a combination therapy (43%) or monotherapy (57%). However, there was no significant discrepancy between the weekday and weekend groups in hemostatic tool usage, and rebleeding rate did not differ with regard to the applied hemostatic method (from 11% to 19%).

The endoscopists who performed the endoscopic hemostasis could be divided into two groups (instructors and hospital staff) according to the level of experience. Among a total 388 subjects, 67% (260 patients) of endoscopic hemostases were performed by hospital staff and the other 33% (128 patients) were performed by instructors. However, there was no significant difference in the level of experience between the weekday and weekend group, and between the daytime and nighttime group (proportion of procedures by hospital staff was 68% in the weekday group vs 59% in the weekend group, P = 0.14; 69% in the daytime group vs 58% in the nighttime group, P = 0.11). Also the rate of rebleeding was not different between the two groups (instructors and hospital staff).

Most patients (97%) underwent early endoscopy regardless of weekend or nighttime admission. Overall, the mean time interval between presentation to the ER and endoscopy was 333.8 ± 22.2 min. The time to endoscopy was slightly shorter in the weekend group, although the difference was not significant (338.9 ± 24.9 min in the weekday group vs 306.8 ± 45.6 min in the weekend group, P = 0.56) (Table 1). However, when time to endoscopy was compared between the daytime group and the nighttime group, it was significantly shorter in the nighttime group (352.9 ± 26.3 min in the daytime group vs 255.0±30.0 min in the nighttime group, P = 0.016) (Table 2).

Mortality: The overall mortality rate was only 1.8% (7/388). The subgroup that had high Rockall scores (≥ 6) included 146 patients, and their mortality rate was 4.1% (6/146). There was no significant difference in mortality between the weekday and weekend groups (1.8% in the weekday group vs 1.6% in the weekend group, P = 0.902) (Table 1). In addition, the mortality rate did not differ between the daytime and nighttime groups (1.9% in the daytime group vs 1.3% in the nighttime group, P = 0.757) (Table 2). All deaths occurred in patients with comorbidities, who had significantly higher CACI (7.0 ± 0.7) and Rockall scores (7.6 ± 0.6) than surviving patients (P < 0.001). The significant risk factors for mortality were age, comorbidity, Rockall score, and Charlson score (Table 3).

Rebleeding: The level of experience did not affect the rate of rebleeding (16% in procedures by instructors vs 14% by hospital staff, P = 0.39) in our study. Age-adjusted analysis revealed a significantly higher rebleeding rate in the weekend group (12% in the weekday group vs 21% in the weekend group, P = 0.030) (Table 1). In addition, despite earlier endoscopy, the rate of rebleeding was also higher in the nighttime group, which we called the nighttime effect, than in the daytime group (11.5% in the daytime group vs 21.1% in the nighttime group, P = 0.018) (Table 2). When the rebleeding rate was compared between the four subgroups that were divided by weekday/weekend and daytime/nighttime, the highest rebleeding rate, which reached up to one third of the patients, was noted in the weekend-nighttime group (11.4% in the weekday daytime, 15.1% in the weekday nighttime, 12.8% in the weekend daytime, and 34.8% in the weekend nighttime, P = 0.040) (Table 4).

Multivariate logistic regression was used to analyze potential factors that affected the in-hospital rebleeding rate. The significant independent risk factors for rebleeding were a high Rockall score (≥ 6) and nighttime rather than weekend admission (Table 5). Therefore, statistically, the risk factor associated with rebleeding was not weekend but nighttime admission.

Length of stay: Age-adjusted analysis revealed a shorter length of stay in the weekend group (8.5 d in weekday vs 6.2 d in weekend, P = 0.009). However, linear regression analysis revealed that the length of stay was not associated with age or weekend admission, but was strongly associated with the type of comorbidity, which correlated well with the CACI. The length of stay increased in proportion to the increase in the CACI.

Upper gastrointestinal bleeding (UGIB) is a common medical emergency and timely endoscopy plays an important role in hemostasis. The “weekend effect” which means a worse outcome in UGIB patients following weekend admission, has been suggested by previous reports, but remains controversial.

Some authors have suggested a weekend effect on UGIB resulting in higher mortality and more frequent surgery. One report suggests that early endoscopy can prevent the weekend effect and reduce mortality, however, contrary results have also been reported. The issue of the weekend effect on UGIB should be whether early endoscopic hemostasis even at weekends can prevent worse outcomes.

The study analyzed various endoscopic and clinical data from 4 centers which can affect the outcome of UGIB. From their results, they can suggest that early endoscopy for peptic ulcer bleeding, even at weekends, can almost prevent the weekend effect. The most important risk factor for rebleeding was a high Rockall score, however, nighttime admission was also identified as a novel risk factor for rebleeding, namely the nighttime effect.

Although early endoscopy for peptic ulcer bleeding can prevent the weekend effect in patients with peptic ulcer bleeding, nighttime presentation and high Rockall score were significant risk factors for rebleeding. The authors need to be more careful and alert when dealing with peptic ulcer bleeding, especially in patients who present at nighttime and those with high Rockall score.

Weekend effect: The weekend effect has previously been reported as worse outcomes in UGIB patients following weekend admission, such as higher mortality and more frequent surgery; Nighttime effect: The nighttime effect is a novel term used in the current study, which means worse outcome due to a higher rebleeding rate in patients with peptic ulcer bleeding following nighttime admission.

This is a well-written manuscript of a retrospective multi-center study investigating the weekend and the nighttime effect on the outcomes of patients with upper GIB requiring endoscopic hemostasis. The results were clearly presented and the contents are easily comprehensible.