A study of more than 15 million hospital admissions in the UK has revealed that patients admitted Friday through Monday face as much as a 15 percent higher relative risk of death. The analysis, published in The British Medical Journal, reiterates findings of earlier UK studies into this so-called "weekend effect." Although the new research doesn't investigate the cause of the higher 30-day mortality rate, it does note that support services in UK hospitals are usually reduced "from late Friday through the weekend, leading to disruption on Monday morning." A similar effect has been observed in US hospitals.

The data was controlled for patients' age and level of sickness

The study found that the highest relative increase in the risk of death was for patients admitted on a Sunday (up 15 percent). This figure was 10 percent higher for Saturday, 5 percent higher for Monday, and 2 percent higher for Friday. During the year studied (from 2013 to 2014) there were 15.9 million hospital admissions, with 290,000 of these patients — 1.8 percent of the total— dying within 30 days. The data was controlled for factors including patients' age and level of sickness, with the authors finding that around 11,000 extra deaths occurred at the weekend compared to the rest of the week. Patients already in hospital over the weekend did not have an increased chance of death.

The authors note that it shouldn't be assumed that this higher mortality rate is avoidable, although experts in the UK medical world have said the study shows change is needed. Clare Marx, president of the Royal College of Surgeons, said in a press statement that it was "clear" that "patients that need treating at the weekend are less likely to be seen by the right mix of junior and senior staff and experience reduced access to diagnostics."

The study feeds into an ongoing debate between politicians and doctors in the UK about hospital service at the weekends, with politicians demanding more weekend hours, and the British Medical Association (BMA) responding that extra money is needed. Dr Mark Porter, head of the BMA, toldBBC News: "Given the current funding squeeze on NHS Trusts, the only way for many hospitals to increase the number of doctors over the weekend would be to reduce the number providing care during the week."

Correction: The original headline for this story suggested a causal link between weekend hospital admissions and death. It has been changed to reflect the results of the study.