The "weekend effect" has been so politically controversial that in the UK the conservative government during the last election pledged to ensure hospitals offered proper diagnostic and other services over the weekend, but there has been little research into the issue in Australia. Study author Paul Aylin, from Imperial College London, said the increase in deaths on the weekends was thought to account for between 3000 and 4000 extra deaths each year in the UK. "A number of possible explanations have been put forward in previous studies, including differences in the types and severity of conditions seen at the weekend, reduced staffing and reduced access to diagnostic and treatment facilities," he said. "Our study attempted to account for the differences in the type and severity of conditions seen, so this is a less likely explanation, but we were unable to look at staffing or access to services within the hospital." He said while the overall risk of death after surgery was low, if he was a patient he "would be interested to know my hospital's policy on staffing levels and senior consultant cover over the weekend". "Our own work around stroke care in the UK suggests that patients admitted at the weekends are less likely to get a same-day brain scan, less likely to get clot-busting treatment and have worse outcomes across a range of indicators," he said.

The study found Australians having surgery on a Tuesday, Wednesday or Thursday were slightly less likely to die within one month of their operation, compared with those who had surgery on a Monday. But the death rate was 20 per cent higher for surgeries performed on a Saturday than on a Monday, and this jumped to 107 per cent for surgeries on a Sunday. While every other country also showed an increased risk of death within one month for people who were admitted to emergency departments on a weekend, in the Australian figures, which only came from six hospitals, this was only evident within a week of admission, not one month later. In this case, the figures showed the risk of death was about 11 per cent greater on the weekends, leading the team to suggest more research was needed, using a greater number of Australian hospitals. University of Adelaide surgical mortality expert Guy Maddern said he believed the weekend effect was real - although he agreed more research taking in more hospitals was needed. "Hospitals tend to have fewer services available over the weekend and fewer staff, so it's not surprising," he said.

But Richard Lilford, a public health professor from the University of Warwick who wrote an editorial on the research also published in BMJ Quality and Safety, said he believed the differences in the type of illnesses suffered by people who had surgery on the weekend could account for most of the difference. "Less than 10 per cent of deaths are preventable, so the preventable death rate would have to double over the weekend to generate the increase seen in overall death rates at the weekend," he said. But he said it was unlikely that the increased deaths among emergency patients would not also be seen in Australia. "I cannot formally exclude that possibility but my prior guess is that such Australian exceptionalism is inherently unlikely," he said.