Researchers suggest attributing the weekend effect to staffing ignores a more complex underlying pattern of weekly changes in quality of care.
The term "weekend effect" arose from research that suggests rates of death are higher among patients admitted to U.K. hospitals at the weekend, compared with those admitted during the week.
Studies on the weekend effect have had a significant effect on health policy and given rise to much controversy and debate.
U.K. policymakers - including the Secretary of State and Department of Health - have stated the weekend effect is caused by a lack of hospital specialists on duty on Saturdays and Sundays, and they are changing doctors' terms of employment to ensure high quality of care is available 7 days a week.
However, the researchers suggest attributing the weekend effect to staffing ignores a more complex underlying pattern of weekly changes in quality of care.
The first study, led by the University of Birmingham in the U.K., finds no link between weekend staffing of senior doctors and risk of death in emergency admissions, and it concludes policymakers should "exercise caution before attributing the weekend effect mainly to differences in specialist staffing."
The second study, led by King's College London and University College London - both in the U.K. - looks specifically at acute stroke care and finds no evidence of a weekend effect on survival.
Instead, it reveals that quality of care varies considerably on a number of levels through the week, and it concludes addressing weekend quality of care on its own is a major oversimplification of the problem that is unlikely to resolve it.
Weekend senior doctors' staffing not linked to risk of death
For the first study, the researchers collected survey data from hospital consultants and clinical service directors on senior doctor input into emergency admissions at 115 National Health Service (NHS) trusts.
The data included the number of hours each doctor spent between 8 a.m. and 8 p.m. caring for patients admitted as an emergency on two days: Sunday 15 and Wednesday 18 June, 2014.
After comparing the survey data with national hospital mortality data, the researchers found substantially fewer senior doctors were available and giving emergency care on the Sunday, compared with the Wednesday (1,667 compared with 6,105).
However, this was partly offset by an average of 40 percent more time spent caring for emergency admissions on Sunday (5.74 hours), compared with Wednesday (3.97 hours).
When the team looked at total admissions per hospital, they found emergency admissions on the Sunday received on average less than half the input of senior doctors, compared with the Wednesday.
Further analysis revealed a small increase in the risk of death linked to weekend admission, but this differed across the NHS trusts, and when risk of death was plotted against availability of senior doctors, there was no link between the two.
The researchers caution that their study did not look at the availability of junior doctors and nurses, nor did it take into account how ill patients were. They note more research is needed to understand the key factors that affect mortality in such a complex system.
Lead author Julian Bion, professor of intensive care medicine at Birmingham, says claiming "lower staffing is the cause for increased mortality is far too simplistic and not supported by the evidence."
'Weekend effect is a major oversimplification'
In the second study, the researchers looked at care data from over 74,000 acute stroke patients admitted to nearly 200 hospitals in England and Wales in the 12 months ending with March 2014. They also examined information about patient survival in the 30 days following admission.
Their analysis showed no difference in the 30-day survival for patients admitted during the day on a Saturday or Sunday, compared with being admitted on a weekday. Evidence that survival was worse for patients admitted overnight was very slight.
However, the researchers found the quality of care patients received varied widely, depending on the day of the week and also the time of day.
For example, arrival in the morning, as opposed to the afternoon, was linked to a higher chance of having a brain scan within an hour. This is consistent with national guidelines.
And patients admitted on a Monday were less likely to be admitted to a stroke unit within 4 hours, while admission on a Thursday or Friday generally meant a longer wait for therapy assessment.
Lead author Dr. Benjamin Bray, a public health academic clinical fellow at University College London, says much of the debate surrounding the weekend effect and how to tackle it overlooks a detailed understanding of why changes in quality of care occur.
"Our study shows that the 'weekend effect' is a major oversimplification of the true extent and nature of variations in the quality of care that occur in everyday practice," explains Dr. Bray, and adds, "Simply transferring doctors from weekdays to weekends is highly unlikely to have the intended effect of improving quality of care."
Comparing weekend with weekdays 'gives skewed results'
The two studies follow an earlier analysis from the University of Manchester, U.K., where researchers suggest comparing death rates at weekends with those of weekdays will give skewed results because emergency departments in England use different rules on weekdays and weekends for deciding whether to admit a patient.
"Hospitals apply a higher severity threshold when choosing which patients to admit to hospital at weekends," says senior author Matt Sutton, professor of health economics at Manchester.
He says their analysis found patients whose illnesses were not serious were not admitted on a Saturday or Sunday, meaning that on average, those admitted at the weekend were sicker than patients admitted during the week and more likely to die regardless of the quality of care available.
Commenting on the three studies, Nick Black, professor of health services research at the London School of Hygiene & Tropical Medicine, U.K., says they raise many points that may help explain the weekend effect, not least that patients are sicker.
"Despite many claims about the quality of care at weekends and strong beliefs about the reasons for this, we need to remain open to the true extent and nature of any such deficit and to the possible causes.
Jumping to policy conclusions without a clear diagnosis of the problem should be avoided because the wrong decision might be detrimental to patient confidence, staff morale and outcomes."
Prof. Nick Black