Patients who undergo pre-planned surgery are more likely to die if their operations are conducted at the end of the week, a new study suggests.
Death rates for elective surgery patients are lowest on Mondays and increase for each subsequent day of the week, researchers said.
The odds of death were 44% higher for patients who had planned operations on a Friday than on a Monday, the study published on bmj.com found.
Researchers, who looked at data concerning more than four million elective procedures conducted in NHS hospitals in England between 2008 and 2011, found that the risk of dying was higher still if the operation was carried out at the weekend.
They found an 82% increased risk if that operation was carried out at the weekend compared to a Monday but stressed that the vast majority of elective procedures are carried out during the working week.
Elective procedures are surgical operations to correct a condition that is not life-threatening, such as hip or knee replacements, cataracts procedures or hysterectomies.
The authors from Imperial College London looked at data concerning patients who had to stay in hospital overnight following their operation. They found that 27,500 patients died within 30 days of their surgery.
The findings could reflect differences in quality of care at the weekend, the authors said.
"The first 48 hours after an operation are often the most critical period of care for surgery patients," said lead author Dr Paul Aylin, from the School of Public Health at Imperial.
"So if the quality of care is lower at the weekend as some previous studies have suggested, we would expect to see higher mortality rates not just for patients operated on at the weekend, but also those who have operations towards the end of the week, whose post-operative care overlaps with the weekend. That is what we found.
"Unlike previous studies, we included both deaths in hospital and deaths after discharge, so this eliminates a potential bias of counting only in-hospital deaths. We tried to account for the possibility that different types of patients might have operations at the end of the week, but our adjustment made little difference.
"This leaves us with the possibility that the differences in mortality rates are due to poorer quality of care at the weekend, perhaps because of less availability of staff, resources and diagnostic services."
In an accompanying editorial, Canadian experts question whether officials should rethink the scheduling of elective surgery at the weekend.
They wrote: "Although emergency procedures, such as the repair of ruptured aortic aneurysms, cannot be controlled, the scheduling of elective procedures, such as knee replacements, is wholly within our control.
"If weekend care proves to deliver poorer outcomes than its weekday counterpart, it might be argued that elective procedures should not be scheduled at weekends at all."Suggest a correction