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Assumptions used in estimating a population benchmark

The assumptions used to estimate a population benchmark of 0.5% per year for referrals to a smoking cessation service for people having elective surgery are based on the published research on the modelling of the number of people admitted for elective surgery.

Published research

The London Health Observatory (LHO) developed a methodology to estimate the numbers of people who smoke and were admitted for elective surgery in London. This methodology was published in the 2005 report: Preoperative smoking cessation: a model to estimate potential short-term gain and reductions in lengths of stay. The methodology outlined in the report builds on and incorporates previous work published by the LHO in 2004 - Tobacco in London: the preventable burden.

The methodology outlined in these two reports has been followed with some amendments. Some of these were developed with the South West Public Health Observatory (SWPHO), and include amendments made by the NHS Information Centre for health and social care in a similar piece of analysis (appendix C of the report Statistics on Smoking: England, 2007). Commissioners may wish to refer to these original reports alongside the amendments outlined below.

The amendments are:

  • Hospital spells, that is, the time an individual spends in hospital, rather than individuals, were counted.
  • Age and sex-specific smoking prevalence and ex‑smoking prevalence rates were applied to the extracted hospital activity data. The analysis carried out by the LHO used average adult population smoking rates, which may lead to an overestimation of the number of people who are admitted for elective surgery and who smoke. This is because the prevalence of smoking is greater in younger age groups (up to 35 years old) and the prevalence of ex-smoking is higher in people in older age groups who are more likely to be admitted for elective surgery.
  • The relative risks used to calculate the proportion of spells for smoking-related diseases that were attributed to smoking were applied to people aged 35 years and older. This is because the topic-specific advisory group advised that the effects of smoking on admission for smoking-related diseases before this age are unknown, and therefore avoids overestimating the number of people who smoke and are admitted for elective surgery. This approach was adopted by the NHS Information Centre for health and social care in a similar piece of analysis (appendix C of the report Statistics on Smoking: England, 2007).
  • For the population under 35 years and admitted to hospital, we have assumed that the prevalence of smoking is the same irrespective of whether the admission is for a smoking-related or a non-smoking-related disease.
  • Day cases (where the length of hospital stay was less than 1 day) were not removed from the data extract. The analysis carried out by the LHO aimed, in part, to calculate expected reductions in length of stay, so day cases were excluded from their analysis. It is thought that people who smoke and who are admitted for day case surgery may also benefit from preoperative smoking cessation. Within the NICE commissioning and benchmarking tool, commissioners can choose whether or not to include this group of patients in their modelling.
  • Spells where the main procedure was either an OPCS-4 (Office of Population, Censuses and Surveys Classification of Surgical Operations and Procedures, 4th revision) chapter U - diagnostic imaging testing and rehabilitation, or an OPCS-4 chapter X - miscellaneous operations (with the exception of code beginning with X0 or X1), were removed from the data extract.

The results of the analysis suggest that in 2006/07 around 1% of the population who smoke were admitted for elective surgery. This number is likely to vary at a local level depending on the case mix of elective surgery rates and smoking prevalence rates.

Use the commissioning and benchmarking tool to calculate the estimated numbers of people who smoke and who are admitted for elective surgery. To calculate this you will need to know your local smoking and ex-smoking prevalence rates, and the attributable proportion of smoking-related diseases caused by smoking.

Click to view the estimated prevalence of smoking and ex-smoking for each primary care organisation (PCO) based on the age, sex and case mix of people having elective surgery within the PCO in 2006/07. Also provided is the attributable proportion of smoking-related diseases estimated to be caused by smoking. Commissioners should note that the estimates of smoking and ex-smoking have not been adjusted for deprivation and ethnicity. Therefore the results of the modelling using these estimates could underestimate demand in some areas, such as those areas with atypical populations. As described above, population smoking and ex-smoking rates are likely to overestimate demand.

Commissioners may wish to also use the local population prevalence of smoking and ex-smoking in scenario modelling. The prevalence of smoking by PCO can be obtained from the NHS Information Centre for health and social care's Neighbourhood statistics: model-based estimates of healthy lifestyle behaviours at PCO level 2003-05.

Expert clinical opinion

The consensus opinion of the topic-specific advisory group was:

  • Not all people who smoke and are admitted for elective surgery are likely to have their smoking status detected, and therefore be offered a referral for smoking cessation. However, services should aim to detect all cases.
  • Around 50% of those people in whom a positive smoking status is detected may take up the offer of smoking cessation support and around 50% of these (that is, around 25% of those detected) would be expected to have quit smoking at four weeks.

Conclusions

Based on the epidemiological data and other information outlined above, it is concluded that the benchmark for referrals of people having elective surgery to a smoking cessation service is estimated to be around 50% of people who smoke and are waiting for elective surgery, or (based on the national average) around 0.5% of the population aged 15 years and older, per year.

Use the smoking cessation service for people having elective surgery commissioning and benchmarking tool to determine the level of service that might be needed locally and to calculate the cost of commissioning the service using the indicative benchmark and/or your own local data.

This page was last updated: 02 March 2012

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Accessibility | Cymraeg | Freedom of information | Vision Impaired | Contact Us | Glossary | Data protection | Copyright | Disclaimer | Terms and conditions

Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.