Closing hospital accident and emergency (A&E) departments has knock-on effects that lead to more patient deaths, a US study has shown.
Shutting down a local casualty ward can have a significant adverse impact on the fate of patients at nearby hospitals, it is claimed.
Recent closure of an A&E unit increased the death rate of patients admitted to surrounding hospitals by 5%, the research conducted in San Francisco found.
The results come in the midst of a major review of hospital emergency services in England which critics fear will open the door to widespread closures.
Professor Sir Bruce Keogh, medical director of NHS England, who is leading the review, has said that rationalising the current "fragmented" system could drive up standards and save lives.
The American researchers looked at more than 16 million emergency admissions to Californian hospitals between 1999 and 2010.
They found that A&E closures had a "ripple effect" that extended out to nearby hospitals. Patients were 5% more likely to die if admitted to a hospital in the vicinity of a closed unit, and the chances of death were even higher for those with certain high risk conditions.
A&E closures increased the risk of heart attack deaths by 15%, stroke deaths by 10% and sepsis (a life-threatening reaction to infection) deaths by 8%.
The problem was caused by closure increasing pressure on nearby emergency departments (EDs) that found themselves forced to cope with more admissions.
Lead researcher Dr Renee Hsia, from the University of California at San Francisco (UCSF) said: "Emergency department closures are affecting many more patients than previously thought.
"Most importantly, people who live in the area of nearby closures but whose own hospital did not close are still negatively affected by increased wait times and crowding in their own emergency department."
A&E units are suffering the strain of increasing workloads in both the US and UK.
In the US demand for hospital emergency services has soared with around 130 million visits made to A&E departments each year, said the researchers writing in the journal Health Affairs.
Yet the number of emergency departments nationwide had fallen by 6% b etween 1996 and 2009.
During the study period, 48 A&E units closed their doors in California.
Previous research has found that patient death rates increase with longer travel or waiting times, and crowding in emergency wards.
Loss of emergency departments could also cause some patients to delay seeking medical help, leading to conditions becoming less treatable, said the authors.
A&E closures were likely to reduce access to care for communities with vulnerable populations.
"Our findings indicate that disproportionate numbers of ED closures may be driving up inpatient mortality in communities and hospitals with more minority, Medicaid and low-income patients, and contributing to existing disparities in health outcomes," said Dr Hsia.
"These results suggest that health systems and policy makers should consider the ripple effect on communities when they regulate ED closures."