News Release

Latest UK data shows rising age, rates of obesity and comorbidity in surgical patients requiring anaesthesia, increasing the pressure on the already overloaded NHS

Latest data show the average age of patients requiring anaesthesia increased by 2.3 years (from 50.5 to 52.8) over the last decade

Peer-Reviewed Publication


Snapshot survey data from the 7th National Audit Project of the Royal College of Anaesthetists (NAP7) published in Anaesthesia (a journal of the Association of Anaesthetists) reveals an extremely worrying picture of increasing age, rates of obesity, and complexity of surgical patients requiring anaesthesia in the UK.

The snapshot activity survey collected patient-level data from all cases under the care of an anaesthetist in UK hospitals delivering anaesthesia in November 2021. Anaesthetists recorded details of all cases undertaken over four days at their institution through an online survey capturing anonymous patient characteristics and anaesthetic details. Of 416 hospital sites invited to participate, 352 (85%) completed the activity survey. A total of 24,172 reports were included in the final dataset. This new research is the first set of results available from NAP7, with the full report due to be published in November 2023.

This paper has been produced by a team of authors across UK hospitals including; Dr Andrew Kane, Fellow, Health Services Research Centre, Royal College of Anaesthetists, London, UK; and Dr Jasmeet Soar, Consultant in Anaesthesia and Intensive Care Medicine, Southmead Hospital, North Bristol NHS Trust, Bristol, UK; and Professor Tim Cook, Consultant in Anaesthesia and Intensive Care Medicine, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK, and Honorary Professor, School of Medicine, University of Bristol.

Patients requiring anaesthesia are older

While the authors found that working patterns in terms of day of the week, time of day and surgical specialties were similar to previous NAP reports, some worrying trends were evident. Between the NAP5 (2013) and NAP7 (2021) surveys and excluding those patients who were pregnant, the estimated median age of patients increased by 2.3 years (50.5 to 52.8 years).

Dr Andrew Kane, lead author says: “The fact that the population requiring surgery with anaesthesia is 2.3 years older than nine years ago has important implications. Although this may seem a modest increase in age, the all-cause mortality in the general population increases approximately 10% for each year of advancing age and doubles as age increases 6–7 years; and thus a 2.3-year increase in age equates to an approximately 27% increase in all-cause mortality. This increase in age is likely to interact with peri-operative risk, most notably for those patients who are elderly, meaning that morbidity, mortality and healthcare costs might all be expected to have risen.”

A higher proportion of patients are living with overweight and obesity

The median BMI of patients increased from 24.9 kg/m2 (the borderline of what is classified as normal weight and overweight) to 26.7 (overweight). On this, the authors say: “We are seeing an increase in both the proportion of patients who are living with obesity presenting for anaesthesia and surgery and in the extent of the obesity. Just 10 years ago, the median BMI of the surgical population was at the top of the 'normal' BMI category, and now in NAP7 it is 'overweight' – such that it is hard to argue that normal weight is indeed still normal. While the proportion of overweight patients in this survey is consistent with the population as a whole, the proportion of  patients living with obesity is higher: patients with a BMI over 30 kg/m2 now represent 1 in 3 patients presenting to anaesthetists. This increase is most marked in obstetric patients who require anaesthetic care to assist childbirth.”

Surgical cases are becoming more complex

Anaesthetists and surgeons use the ASA (American Society of Anesthesiology physical status) scale to provide a measure of the complexity/comorbidity of surgical patients where 1 is the least complex and 5 the most complex. The proportion of patients scored as ASA 1 (least complex) decreased from 37% in NAP5* (2013) to 24% in NAP7 (2021). The proportion of patients with an ASA score of 2 (with controlled long term health issues such as high blood pressure or diabetes) increased from 39% in NAP5 to 45% in NAP7. The proportion of patients who scored ASA 3 (such as those who have had a previous heart attack or stroke) increased from 18% in NAP5 to 25% in NAP7, while the proportion of very high risk (ASA 4) patients was similar (3% in NAP 5 / 4% in NAP7). The authors believe these numbers represent actual changes in the patient mix presenting to NHS hospitals for surgery.

Anaesthesia is reducing its carbon footprint

The survey also examined anaesthetic techniques in use, and highlights a dramatic increase in the use of ‘greener’ anaesthetic techniques. Administering anaesthesia with an intravenous infusion of drugs, is a more sustainable technique than traditional methods using anaesthetic ‘gases’ as it avoids use of volatile anaesthetics and nitrous oxide all of which are potent greenhouse gases. Over the last decade the use of intravenous anaesthesia has tripled from 8% to 26% delivering a more ‘climate friendly’ anaesthesia.

Implications for patient waiting lists and the healthcare workforce

The survey was taken as a snapshot of activity during a year in which surgical activity was still affected by COVID-19. The authors comment that this might alter extrapolations in terms of absolute case activity but does not alter the findings reported here.

Dr Soar says: “These data show increasing age, obesity and comorbidity trends leading to an increasingly complex peri-operative workload. The extent to which these trends would have occurred without the COVID-19 pandemic is unclear, but they must be addressed in this new post-pandemic era.”

Prof Cook adds: “This study shows important patient changes that all increase the workload of anaesthetic, surgical and perioperative teams. Patients undergoing anaesthesia and surgery in the UK have, over the last decade, become older, more likely to be living with obesity and more medically unwell. All these factors interact to make anaesthetic and surgical care more complicated and higher risk. Safely managing patients with these characteristics requires more time in the operating theatre and can lead to slower recovery and more complications after surgery, both of which can require a longer time spent in hospital. These trends are a threat to current efforts to reduce the huge surgical waiting list. Any increases in the trends we have seen in this report will add to pressures on hospital services and we need to make national efforts to get patients fitter for surgery.”

Dr Fiona Donald, President of the Royal College of Anaesthetists said: “These results confirm that what we have observed in our day-to-day work caring for patients is a nationwide trend. It is a worrying picture, but there are things that we can do to better prepare many patients for their operation through greater emphasis on perioperative care. We can help patients by supporting them to improve their health while they are waiting, for example through access to smoking cessation services and providing practical advice on changes to diet and exercise that can make a big difference.”  

Professor Tim Cook, Consultant in Anaesthesia and Intensive Care Medicine, Royal United Hospitals Bath NHS Foundation Trust, Bath, UK and Honorary Professor University of Bristol, UK. T) +44 (0)7970 025209 E)

Dr Andrew Kane, Fellow, Health Services Research Centre, Royal College of Anaesthetists, London, UK. Interview requests via Royal College of Anaesthetists (RCoA) Press Office. T) +44 20 7092 1533 / +44 7711 767377 (out of hours) E)

Dr Jasmeet Soar, Consultant in Anaesthesia and Intensive Care Medicine, Southmead Hospital, North Bristol NHS Trust, Bristol UK. Please e-mail to arrange interview. E)


Dr Fiona Donald, President, Royal College of Anaesthetists. Please contact via the RCoA press office: T) +44 20 7092 1533 / +44 7711 767377 (out of hours) E)

Dr Matt Davies, President of the Association of Anaesthetists. Please contact via e-mail. E)


Alternative contact: Tony Kirby of Tony Kirby PR. T) +44 7834 385827 E)

For full embargoed paper, click here


Note that this paper includes the first results from NAP7, the complete report will be published in November 2023 (date to be confirmed). The Royal College of Anaesthetists National Audit Projects study rare but potentially serious complications related to anaesthesia. They are intended to examine, report on and drive improvements in practice and are delivered by the NIAA Health Services Research Centre (HSRC), the national centre of excellence for health services research in anaesthesia and associated specialties. Each NAP focuses on a different topic important to patients and anaesthetists. NAP7 is examining perioperative cardiac arrest.  

For NAP5 report from 2013, see:

(for ASA data in this release see table 6.3 page 38)



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