At the heart of every good health system is one that provides good emergency care. Yet, in the past 15 years there has been a 50% increase in the number of people being admitted to hospital in an emergency. This is stressful for patients, and puts a great strain on hospitals’ resources. Last year, the NHS recorded almost six million emergency admissions to hospitals, representing around 70% of all hospital bed days in England and costing in excess of £16bn.

Recent policies, from the Better Care Fund to the New Models of Care and Sustainability and Transformation Programmes, have aimed to reduce the rate of growth in emergency admissions, for example, by concentrating on those that might be ‘avoidable’ through better care out of hospital. But it is not entirely clear what is driving this rising demand. A common line is that emergency admissions have been driven up by the rise in the population of over 65s, as they are the more likely users. However, when we look at the statistics, the number of over 65s has increased by only half the growth rate of emergency admissions. Numerous studies show that demographic trends and population health are able to explain only 40-50% of the total growth.

With the aim of shedding some light onto this puzzle, we planned a new study and gained support from the Health Foundation within the Value for money in the English NHS research initiative. As with many new studies, we tried to be original and look where others haven’t already. We searched for other big changes in the health system that might have a logical relationship with the use of emergency care.  

Without having to look too far, for too long, we found that in the past hospitals have achieved remarkable improvements in the survival rates of their patients by investing in new medical technologies, adopting more effective surgical interventions and implementing new policies on patient safety.  A growing number of patients with acute life-threatening conditions survive after surgery. However, an unintended consequence of this success may be a growing population of patients who are increasingly frail and at high risk of more hospital admissions over time.

We investigated this hypothesis by using a very large dataset including nine million patients with a first hospital admission for an acute event, such as a heart attack or a stroke. We then followed these patients for up to two years from the first acute event, counting the times they were back for an emergency admission for any reason and to any hospital.

We repeated this exercise every year from 2000 to 2009 and found that, in every year, more patients survived their first admission than in the previous year and all surviving patients experienced a greater number of emergency admissions following the first acute event. Our analysis found that patients admitted in hospitals with larger improvements in their survival rates experienced increased numbers of emergency admission following the first acute event.  

When applying this to the total growth in emergency admissions observed between 2000 and 2009 in our sample, we found that improvement in survival accounted for about 37% of the total increase in emergency admissions.

These findings have some interesting implications when applied to the whole population of NHS patients. The survival effect led to an estimated increase of 426,000 emergency admission in 2012 and remained at this higher level thereafter, costing a total of about 1 billion in hospital services every year. This estimate does not include the effect of further improvements in survival which are likely to have occurred after 2009.

Emergency care services of the NHS and many other health systems are coming under significant pressure and there is a need for additional resources to cope with an increasing demand for services. A sizeable part of emergency admissions and their cost can be explained by the success of NHS hospitals in saving more patients with life-threatening conditions.

Finally, policymakers have adopted a series of measures to contain emergency admissions. The measures share the common view that a significant proportion of admissions are avoidable and are often driven by hospitals’ financial incentives and inefficiencies. However, current policies may generate unwanted consequences for the health system, draining resources from virtuous hospitals that are succeeding in saving their patients’ lives.

Dr Mauro Laudicella is a Senior Lecturer in Health Economics in the School of Health Sciences at City, University of London, @MLaudicella.