Patients admitted to hospital at the weekend face a higher risk of death in several developed countries, according to new research.

The so-called ‘weekend effect’ has previously been identified in England by Imperial researchers, but the new study reveals that it is also evident in Australia, the USA, and the Netherlands.

Publishing their findings in BMJ Quality & Safety, the researchers say the international nature of the findings suggests that the causes are common to many health systems.

The researchers looked at data on almost three million admissions between 2009 and 2012 from 28 metropolitan teaching hospitals in the four countries.

They focused on deaths occurring in hospital within 30 days of an emergency admission or elective surgery.

They found that, after taking account of patient factors, the risk of dying within 30 days was higher for emergency admissions at weekends for hospitals in three out of the four countries. This risk was eight per cent higher in England, 13 per cent higher in the US, and 20 per cent higher in the Netherlands.

There was no significant daily variation in the risk of death after 30 days for emergency admissions at weekends in the Australian hospitals, and these hospitals between them had the largest proportion of emergency admissions. However, a weekend effect became apparent when looking at deaths with seven days.

All patients admitted at the weekend for planned surgery were more likely to die within 30 days across the board than those admitted on other days of the week.

Furthermore, the data indicated a ‘Friday effect’ for elective patients in the selected hospitals in the Netherlands: their risk of death was 33 per cent higher if admitted on a Friday than on a Monday.

“Although these results are limited to the small number of participating hospitals, the international nature of our database suggests that this is a systematic phenomenon affecting healthcare providers across borders,” said Professor Paul Aylin, who led the research, at the School of Public Health at Imperial College London.

The researchers speculate on the reasons for the findings, pointing out that no one single factor is likely to be responsible.

They suggest that certain diagnoses and procedures may be particularly sensitive to reduced access to test results and diagnostics at weekends. Similarly, weekend staff may be fewer in number and less experienced, while patients requiring urgent care may have to wait longer, which might affect the success of any treatment and interventions. 

Reference: ‘The Global Comparators project: international comparison of 30-day in-hospital mortality by day of the week.’ BMJ Quality & Safety doi 10.1136/bmjqs-2014-003467