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The weekend effect—how strong is the evidence?

BMJ 2016; 353 doi: http://dx.doi.org/10.1136/bmj.i2781 (Published 19 May 2016) Cite this as: BMJ 2016;353:i2781
  1. Jacqui Wise, freelance journalist, London, UK
  1. jacquiyoung1{at}gmail.com

Jacqui Wise looks at recent research on the increased risks for patients admitted at the weekend and asks leading experts to point out where there is consensus and where there are gaps

The health secretary, Jeremy Hunt, has cited various evidence to support the government’s push to improve hospital services on Saturdays and Sundays and to justify imposing new contracts on junior doctors.1 2 3 4 5 6 But as the junior doctors strike has rolled on, studies on the so called weekend effect—excess deaths in people admitted to hospital at weekends—have become political footballs used by all parties to justify their positions, leading to confusion about what the evidence really shows.

Of the 15 substantive studies dominating public debate (the 11 Hunt refers to and four new papers, including one published in The BMJ this week), none has reached definitive conclusions about the cause of the weekend effect , and two recent studies have even questioned whether there is a weekend effect at all. No study has specifically looked at whether the numbers of junior doctors on duty at weekends affects outcomes. Those that have looked at senior doctor staffing have reached mixed conclusions. And there are many potential contributing factors that have so far received little attention.

So should policy makers wait for more comprehensive evidence? Or is it obvious what needs to be done? Is there a risk that the government pushes on with its plan for enhanced seven day services only to find the weekend effect remains?

Is there a “weekend effect”?

Are patients admitted to hospital at weekends more likely to die than those admitted on week days? The study findings are divided.


Aylin et al. Weekend mortality for emergency admissions: a large multicentre study. BMJ Quality and Safety 2010;19:182-6; doi:10.1136/qshc.2008.028639

The adjusted odds of death for patients admitted on a Saturday or a Sunday to all public acute hospitals in England were 10% higher in the following 30 days than those admitted on weekdays.

Freemantle et al. Weekend hospitalisation and additional risk of death: an analysis of inpatient data. Journal of Royal Society of Medicine 2012;105:74-84; doi:10.1258/jrsm.2012.120009

Admission to any NHS hospital at the weekend was associated with a significantly increased risk of in-hospital death within 30 days compared with admission on a Wednesday. But the likelihood of actually dying on a weekend day was less than on a mid-week day.

Aylin et al. Day of week of procedure and 30 day mortality for elective surgery: retrospective analysis of Hospital Episode Statistics. BMJ 2013;346:f2424; doi:10.1136/bmj.f2424

The adjusted odds of death for patients who had surgical procedures at acute and specialist English hospitals on a Friday or at the weekend were 44% and 82% higher, respectively, compared with patients who had these procedures on a Monday.

Ruiz et al. The Global Comparators Project: international comparison of 30 day in-hospital mortality by day of the week. BMJ Quality and Safety 2015;24:480-2; doi:10.1136/bmjqs-2014-003467

Mortality was higher among patients admitted over the weekend in most of the hospitals studied in England, Australia, the United States, and Netherlands.

Freemantle et al. Increased mortality associated with weekend hospital admission: a case for expanded 7 day services? BMJ 2015;351:h4596; doi:10.1136/bmjh4596

Emergency and elective patients admitted to all NHS hospitals at the weekend were 10% sicker and faced a 15% increased relative risk of death within 30 days compared with those admitted on week days.


Li and Rothwell. Biases in detection of apparent “weekend effect” on outcome with administrative coding data: population based study of stroke. BMJ 2016;353:i2648; doi:10.1136/bmj.i2648

Coding errors for stroke patients in Oxfordshire distort the mortality figures, making them appear better for patients admitted on weekdays.

Bray et al. Weekly variation in health care quality by day and time of admission: a nationwide, registry-based, prospective cohort study of acute stroke care. Lancet 2016 doi:10.1016/S0140-6736(16)30443-3

No difference in 30 day survival between weekends and weekdays. However, mortality among patients admitted at night was 10% higher than among those admitted during the day.

What the critics say

Derek Bell, professor of acute medicine, Imperial College London, says: “The majority of the published literature shows a weekend effect, especially large studies. Emergency patients seems to be most affected, and medical probably more than surgical, rather than elective.”

Nick Black, professor of health services research at the London School of Hygiene and Tropical Medicine in London says: “All studies that are based on Hospital Episode Statistic (HES) data suffer from the problem that you can’t adjust adequately for case mix. There is nothing in the coding about comorbidity.”

Is mortality the right thing to focus on?

Palmer et al. Dying for the weekend: a retrospective cohort study on the association between day of hospital presentation and the quality and safety of stroke care. Archives of Neurology 2012;69:1296-302; doi:10.1001/archneurol.2012.1030

Patients with stroke admitted to English hospitals at weekends are less likely to receive urgent treatments such as brain scans (43.1% v 47.6% in the week) or thrombolysis and have worse outcomes across a range of indicators (11% compared with a mean of 8.9% in the week).

What the critics say

Andrew Goddard, former director of the Royal College of Physicians’ medical workforce unit: “Mortality tends to make headline figures, but it is a blunt tool and needs studies with very large numbers. We shouldn’t really be using it as a marker of quality of care; there are much more sensitive markers.”

Is inadequate staffing the problem?\

Aiken et al. Nurse staffing and education and hospital mortality in nine European countries: a retrospective observational study. Lancet 2014;383:1824-30; doi:10.1016/S0140-6736(13)62631-8

An increase in a nurses' workload by one patient increased the chances of an inpatient dying after common surgery within 30 days of admission by 7%, and every 10% increase in nurses with a bachelor degree was associated with a 7% decrease in this likelihood.

Ruiz et al. Exploring the impact of consultants’ experience on hospital mortality by day of the week: a retrospective analysis of hospital episode statistics. BMJ Quality and Safety 2015; doi:10.1136/bmjqs-2015-004105

Death rates among patients admitted for elective surgery were higher on Friday, Saturday, and Sunday but consultant seniority had no significant effect on predicting mortality. Patients operated on by junior consultants had slightly lower odds of 30 day death than those operated on by more experienced consultants. Consultants working on a Friday tended to have the fewest years’ experience.

Palmer et al. Association between day of delivery and obstetric outcomes: observational study BMJ 2015;351:h5774; doi: 10.1136/bmj.h5774

Babies born at the weekend had an increased risk of being stillborn or dying in hospital within the first seven days. But the study found no consistent association between outcomes and staffing.

Ozdemir et al. Mortality of emergency general surgical patients and associations with hospital structures and processes. British Journal of Anaesthesia 2015;116:54-62; doi:10.1093/bja/aev372

Data from 156 NHS trusts showed that those with fewer general surgical doctors and lower nursing staff ratios had higher mortality among patients admitted at weekends.

Aldridge et al. Weekend specialist intensity and admission mortality in acute hospital trusts in England: a cross-sectional study. Lancet 2016; doi:10.1016/S0140-6736(16)30442-1

Patients received only half as much specialist attention at weekends as on weekdays. The survey of 15 000 specialists found a 10% increase in the risk of death associated with weekend admission but no evidence of an association between senior doctor staffing and mortality. The response rate for this study was only 45%.

What the critics say

“Weekend mortality is higher, and staffing is lower, and while association is not causation, the studies point to more resources being linked to better outcomes, which is plausible and intuitive,” says Rubin Minhas, clinical director of the BMJ Evidence Centre.

Andrew Goddard, former director of the Royal College of Physicians’ Medical Workforce Unit, says: “There is no great correlation between senior staffing levels at weekends and mortality. There also haven’t been any good studies looking at the effect of numbers of medical registrars at the weekend. Part of the difficulty is that there are so many different models of care between different hospitals and different wards regarding staffing.”

Paul Aylin, codirector of Dr Foster Unit at Imperial College London, commented: “A higher proportion of junior consultants are operating on a Friday. It looks as though junior consultants have lower mortality but this may be because they tend to do less complex cases.”

Are patients admitted at weekends sicker?

Mickulich et al. The increased mortality associated with a weekend emergency admission is due to increased illness severity and altered case mix. Acute Medicine 2011;10:182-7

Although patients admitted at the weekend to one Dublin hospital had a roughly 11% higher 30 day in-hospital mortality compared with those admitted on weekdays, the case mix was different (for example, more neurological diagnoses and less gastrointestinal disease). Once this was accounted for there was no increased mortality at the weekend.

Freemantle et al. Increased mortality associated with weekend hospital admission: a case for expanded 7 day services? BMJ 2015;351:h4596; doi:10.1136/bmjh4596

More patients admitted at the weekend are more seriously ill than those admitted in the week, but even when results are adjusted to account for this, there is still an increased relative risk of death of 15%.

Meacock et al. Higher mortality rates amongst emergency patients admitted to hospital at weekends reflect a lower probability of admission. Journal of Health Service Research and Policy 2016; doi:10.1177/1355819616649630

The daily number of admissions at 140 trusts in England from emergency departments was similar at weekends to that on weekdays, but the number of direct admissions from the community was 61% lower. While mortality for admissions via emergency departments was only 5% higher at weekends, for direct admissions it was 21% higher.

What the critics say

Minhas asks: “Is the weekend association really just the clustering of different risk groups of patients across the week, rather than anything to do with hospital care?”

Bell says: “The issue of illness severity being different at weekends is often suggested but not really backed up by well conducted studies, and even if this were the case we would need to ensure services overall are even better able to cope.”

Studies examining the weekend effect

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  • Competing interests: I have read and understood BMJ policy on declaration of interests and have no relevant interests to declare

  • Provenance and peer review: Commissioned; not externally peer reviewed.

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