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Effect of day of the week on short‐ and long‐term mortality after emergency general surgery. BJS 2017; 104: 936-945.

Published: 21st March 2017

Authors: M. A. Gillies, N. I. Lone, R. M. Pearse, C. Haddow, L. Smyth, R. W. Parks et al.


The effect of day of the week on outcome after surgery is the subject of debate. The aim was to determine whether day of the week of emergency general surgery alters short‐ and long‐term mortality.


This was an observational study of all patients undergoing emergency general surgery in Scotland between 1 January 2005 and 31 December 2007, followed to 2012. Multilevel logistic and Cox proportional hazards regression were used to assess the effect of day of the week of surgery on outcome after adjustment for case mix and risk factors. The primary outcome was perioperative mortality; the secondary outcome was overall survival.


A total of 50 844 patients were identified, of whom 31 499 had an emergency procedure on Monday to Thursday and 19 345 on Friday to Sunday. Patients undergoing surgery at the weekend were younger (mean 45·9 versus 47·5 years;
P < 0·001) and had fewer co‐morbidities, but underwent riskier and/or more complex procedures (P < 0·001). Patients who had surgery at the weekend were more likely to have been operated on sooner than those who had weekday surgery (mean time from admission to operation 1·2 versus 1·6 days; P < 0·001). No difference in perioperative mortality (odds ratio 1·00, 95 per cent c.i. 0·89 to 1·13; P = 0·989) or overall survival (hazard ratio 1·01, 0·97 to 1·06; P = 0·583) was observed when surgery was performed at the weekend. There was no difference in overall survival after surgery undertaken on any particular day compared with Wednesday; a borderline reduction in perioperative mortality was seen on Tuesday.


There was no difference in short‐ or long‐term mortality following emergency general surgery at the weekend, compared with mid‐week.

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Your comments


John Saunders

2 months ago

Dear Sir,

There has been significant scrutiny of the NHS (1) since the seminal publication by Aylin et al. around the weekend effect in surgery (2), so we, as others, read this analysis with some relief following the continual negative publicity (3).

Care needs to be taken when interpreting these different studies, unlike arguments played out by the media (4), as they include different cohorts of patients. The paper by Aylin et al. included five high-risk patient groups undergoing elective surgery. The ‘weekend effect’ has since been demonstrated in other studies considering elective surgery (5). It should be realised that cohorts undergoing elective surgeries over a weekend are likely to be inherently different.

The current paper focuses on emergency surgery in Scotland. Analysis of patients undergoing emergency laparotomy in England demonstrated poorer outcomes when operated on at the weekends, and, intriguingly, with no weekend effect seen in similar patients in the USA (6).

If the differences between these studies and the current study are not a result of data artefacts, case mix and/or coding errors, this raises an interesting hypothesis: is the ‘weekend effect’ only seen in certain health care systems? If this is the case, studying the systematic differences in health care provision may provide an understanding of the variations in outcomes seen.

In England, the High-intensity Specialist-Led Acute Care (HiSLAC) study is attempting to understand the systematic causes between NHS hospitals of the increased mortality rates associated with weekend hospital admission. A qualitative analysis between healthcare systems may also be fruitful.

JH Saunders
RS Vohra

Trent Oesophago-Gastric Unit
Nottingham City Hospital
Nottingham University Hospitals NHS Trust
Nottingham, NG5 1PB

1. McKee M. The weekend effect: now you see it, now you don’t. Bmj. 2016;353:i2750.
2. Aylin P, Alexandrescu R, Jen MH, Mayer EK, Bottle A. Day of week of procedure and 30 day mortality for elective surgery: retrospective analysis of hospital episode statistics. Bmj. 2013;346:f2424.
3. Crump H. Seven day working: why the health secretary’s proposal is not as simple as it sounds. Bmj. 2015;351:h4473.
4. BBC. http://www.bbc.com/news/uk-scotland-39340745. 2017.
5. Vohra RS, Pinkney T, Evison F, Begaj I, Ray D, Alderson D, et al. Influence of day of surgery on mortality following elective colorectal resections. The British journal of surgery. 2015;102(10):1272-7.
6. Tan BH, Mytton J, Al-Khyatt W, Aquina CT, Evison F, Fleming FJ, et al. A Comparison of Mortality Following Emergency Laparotomy Between Populations From New York State and England. Annals of surgery. 2016.

Ross McLean

1 month ago

Dear Sir,

We read with interest the analysis by Gillies et al. (1), who highlighted there was no difference in perioperative or overall mortality for patients undergoing emergency general surgery by day of the week of admission or operation in Scotland between 2005-2007. Specifically, they found no evidence of a “weekend effect” for mortality.

Gillies et al. confirm McCallum et al.’s (2) findings that patient case mix is different at weekends (younger, more male and fewer co-morbidities (1,2)), and support that processes of care may also be optimised at weekends; for example, shorter times to theatre. Ozdemir et al. (3) showed a ‘weekend effect’ for day of admission between 2005-2010. McCallum et al. showed a historical “weekend effect” for day of operation between 2005-2009 but in their most recent analysis period (2010-2014) there was no evidence of a “weekend effect”.

When scrutinizing Gillies et al.’s methodology, we have concerns regarding their Operation Code inclusion criteria compared with other similar studies (2,3). They have included skin and soft tissue, urology, vascular and plastic/orthopaedic procedures in their most common procedures (Supplementary Table S1 and S2). These operations within the “general surgery” case mix include very low risk procedures which are non-general surgical (for example: tendon repairs, skin grafts, skin suturing) and will tend to underestimate overall mortality risk and may mask the influence of clinical factors (weekend effect, age, gender, etc.) on general surgical patients. We would advocate exclusion of these patients from the dataset, since they have an impact on the multivariate analysis; for example, within Supplementary Tables S4, S6, S8, and S10, all other procedure categories (other, skin and soft tissue and urology) have a higher hazard of mortality than GI procedures which was the referent procedure. This is very much at odds with clinical common sense.

The study population therefore dilutes the analysis of high risk emergency abdominal procedures that we assume to be the focus of a paper on emergency “general surgery”. We are concerned that a “weekend effect” which has been shown to be present at that time in other studies may have been missed in their analysis. Concerns have already been raised regarding adequate numbers and powering of the study (4), and excluding these inappropriate patients would purify the general surgical patient group, but lose statistical powering.

Ross McLean
Iain McCallum
Paul O’Loughlin

Unit of Colorectal Surgery
Queen Elizabeth Hospital
Gateshead, NE9 6SX

1. Gillies MA, Lone NI, Pearse RM, Haddow C, Smyth L, Parks RW, et al. Effect of day of the week on short- and long-term mortality after emergency general surgery. Br J Surg 2017. http://doi.wiley.com/10.1002/bjs.10507
2. McCallum IJD, McLean RC, Dixon S, O’Loughlin P. Retrospective analysis of 30-day mortality for emergency general surgery admissions evaluating the weekend effect. Br J Surg 2016; 103: 1557–1565.
3. Ozdemir BA, Sinha S, Karthikesalingam A, Poloniecki JD, Pearse RM, Grocott MPW, et al. Mortality of emergency general surgical patients and associations with hospital structures and processes. Br J Anaesth 2016; 116: 54–62.
4. Hawkes N. Weekend emergency surgery is no riskier than operations during week, study finds. BMJ 2017; j1473.