Patients are more likely to die in hospital at weekends than on weekdays, according to ground-breaking Australian research that experts say shows hospital staffing levels must change.
They say continuing to operate on a five-day week business model will put lives at risk.
"Illness occurs 24/7, not just in normal business hours,'' said lead author Enrico Coiera, the director of the Centre for Health Informatics at the University of NSW. ''The idea that we can offer reduced levels of care at the weekend needs to be re-evaluated.''
The first Australian study into the so-called ''weekend effect'' confirms some patients are up to 15 per cent more likely to die if they have been admitted via the emergency department from midnight on Friday until midnight on Sunday.
But a spokeswoman for NSW health said the data had several limitations. These included ''the absence of other important explanatory data such as severity of illness within each diagnostic group, consideration of when the patient's procedure was performed, and consistency in the way each patient's case was recorded.''
When it comes to specific diseases - including heart attack, stroke and some cancers - 1101 more deaths occurred in NSW at the weekend from 2001-07 than expected, Professor Coiera said.
Excessive death rates could be the result of low staffing levels and reduced quality of care, he said.
''We think that people who die from acute heart disease aren't getting access to the emergency services they need. And all their risk is jammed into the first 24 hours,'' he said. ''If you're in a city it's more likely you will have access to emergency doctors.
''But in smaller or rural hospitals doctors might be on call. Even a small delay can impact survival.''
The weekend effect also occurs in patients with some types of cancer, the study, published in the journal BMJ Quality and Safety, revealed.
In those patients, including people with lymphoma and lung cancer, weekend deaths are likely to be caused because sicker people are turning up after regular hours, often because they are unable to cope over the weekend.
''If you are feeling unwell, you shouldn't wait until Friday afternoon to go to hospital,'' Professor Coiera said.
The University of NSW study examined 7325 deaths from 917,000 weekend admissions through emergency departments in all 501 NSW public and private hospitals between 2001 and 2007.
Overall, weekends accounted for more than a quarter of all hospital admissions and 28 per cent of deaths.
Similar studies in Britain have indicated that hospitals may rely on junior doctors and nurses to treat critically ill patients at weekends. ''Hospitals still largely operate on a 9-5 business model,'' said Sally McCarthy, spokeswoman for the Australasian College for Emergency Medicine. ''But people can get sick at any time of day or night.''
She said specialists, diagnostic services and senior clinical staff are needed by patients around the clock.
Traditionally, the most senior medical staff are not rostered on weekends, said Brett Holmes, the general secretary of the NSW Nurses and Midwives' Association. ''There are fewer emergency theatres available, reduced radiology and x-ray services and waiting times are increased for people who might need stents after a heart attack.''
He said one nurse for every three patients in emergency departments on weekends and weekdays was essential.
Professor Coiera said most people were surprised the weekend effect exists at all.