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Publication, Part of

Health Survey for England, 2021 part 2

Official statistics, National statistics, Survey

National Statistics

Current Chapter

Data Quality Statement


Data Quality Statement

Background

Context

The Health Survey for England series was designed to monitor trends in the health, and health related behaviours, of adults and children in England. The survey is used to estimate the proportion of people in England who have specified health conditions, and the prevalence of risk factors and behaviours associated with health conditions. The surveys provide regular information that cannot be obtained from other sources. The surveys have been carried out since 1994 by the Joint Health Surveys Unit of NatCen Social Research and the Research Department of Epidemiology and Public Health at UCL.

Purpose of report

This statement aims to provide users with an evidence-based assessment of quality of the statistical output included in this report. 

It reports against those of the nine European Statistical System (ESS) quality dimensions and principles appropriate to this output. In doing so, this meets NHS Digital’s obligation to comply with the UK Statistics Authority (UKSA) Code of Practice for Statistics, and the following principles in particular:

  • Trustworthiness pillar, principle 6 (Data governance) which states “Organisations should look after people’s information securely and manage data in ways that are consistent with relevant legislation and serve the public good.”
  • Quality pillar, principle 3 (Assured Quality) which states “Producers of statistics and data should explain clearly how they assure themselves that statistics and data are accurate, reliable, coherent and timely.”
  • Value pillar, principle 1 (Relevance to Users) which states “Users of statistics and data should be at the centre of statistical production; their needs should be understood, their views sought and acted upon, and their use of statistics supported.”
  • Value pillar, principle 2 (Accessibility) which states “Statistics and data should be equally available to all, not given to some people before others. They should be published at a sufficient level of detail and remain publicly available.”

The Health Survey for England was assessed in 2010 by the UK Statistical Authority (UKSA) for compliance with the Code of Practice and the publication was recommended for continued designation as National Statistics. 
 


Relevance

This dimension covers the degree to which the statistical product meets user needs in both coverage and content.

Each survey in the series includes core questions and measurements (such as blood pressure, height and weight and analysis of blood and saliva samples), as well as some modules of questions that are on specific topics that vary from year to year.
Frequent topics include:

  • height, weight, BMI (body mass index)
  • smoking
  • alcohol
  • fruit and vegetable consumption
  • general health, acute sickness and long-standing illness
  • General Health Questionnaire (GHQ-12) an indicator of probable mental ill health
  • blood pressure and hypertension
  • diabetes
  • prescribed medicines taken
  • well-being
  • physical activity
  • social care for older people

Most of these are included each year in the survey, but some may be every two, three or four years. 

The contents of the publication vary from year to year. Key prevalence measures are included each year and other topics vary to ensure that the wide range of topics is covered over time and also to reflect the inclusion of new topics. The publication includes trends tables reporting on key elements of the survey every year and the longevity of the survey means there is a long time series of comparable data available. It is one of the longest running health surveys across Europe.

NHS Digital regularly consults the HSE Steering Group (consisting of Department of Health and Social Care (DHSC), Office for Health Improvement and Disparities (OHID), NHS England and academics and public health leaders) regarding survey design, content and reporting to try and ensure most users’ needs are met.


Accuracy and reliability

This dimension covers, with respect to the statistics, their proximity between an estimate and the unknown true value.

The figures in this publication come from surveys, which gather information from a sample rather than from the whole population. The sample is designed to be as accurate as possible given practical limitations such as time and cost constraints. Results from sample surveys are always estimates, not precise figures. This can have an impact on how changes in the estimates should be interpreted, especially for short-term comparisons.

As the number of people available in the sample gets smaller, the variability of the estimates that we can make from that sample size gets larger. Estimates for small groups are less reliable and tend to be more volatile than for larger aggregated groups.

As the data are based on a sample (rather than a census) of the population, the estimates are subject to sampling error. The Health Survey for England 2021 used a clustered, stratified multi-stage sample design and in addition, weights were applied when obtaining survey estimates. One of the effects of using the complex design and weighting is that standard errors for survey estimates are generally higher than the standard errors that would be derived from an unweighted simple random sample of the same size. The calculation of standard errors shown in the tables, and comments on statistical significance have been included in the report, all of which have considered the clustering, stratification and weighting of the data.

In general, attention is drawn to differences between estimates only when they are significant at the 95% confidence level, thus indicating that there is less than 5% probability that the observed difference could be due to random sampling variation when no difference occurred in the population from which the sample is drawn.

A total of 5,880 adults (aged 16 and over) and 1,240 children (aged 0 to 15) were interviewed in the 2021 survey. 1,705 adults and 250 children had a nurse visit and measurements. Findings for 2021 are for adults only; findings about children are not included because of low sample numbers within different age groups. Details of the sample design and survey methods and sampling errors and design effects are in the publication’s Methods report which accompanies this publication.

The sample was designed to be representative of the population living in private households in England. People living in institutional settings such as residential care homes, offender institutions, prisons, in temporary housing (such as hostels or bed and breakfasts) or sleeping rough are outside the scope of the survey. This should be borne in mind when considering survey findings, especially those for older people, since the institutional population in care homes is likely to be older and, on average, less healthy than those living in private households. The health of other people not covered by the survey might also vary from that of people in private households in some ways. However, the proportion of these in the England population is very small and so is likely to have little impact on most prevalence estimates.


Timeliness and punctuality

Timeliness refers to the time gap between publication and the reference period. Punctuality refers to the gap between planned and actual publication dates.

A report about the survey findings and trend data tables are published annually and as soon as possible following completion of fieldwork data collection, data validation and analysis. Addresses were issued from January 2021 to March 2022. Fieldwork was completed in June 2022.

Due to the effects of the Covid-19 pandemic and extended data collection period, a decision was made to publish the 2021 HSE report in two parts to ensure timeliness of the data.

This publication has not suffered any delay compared to the planned and preannounced release dates.


Accessibility and clarity

Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the metadata, illustrations and accompanying advice.

From 2021 reports have been published in HTML format, with tables provided in Excel format. Methods and Survey documentation materials are available for download in pdf format.

Approved researchers seeking to undertake secondary analysis of the Health Survey for England will be able to apply for access via the UK Data Service or for access to a more detailed data set via the  NHS Digital’s Data Access Request Service (DARS) and the UK Data Service, more information is available on the Population Health Data Access Webpage.


Coherence and comparability

Coherence is the degree to which data which have been derived from different sources or methods but refer to the same topic are similar. Comparability is the degree to which data can be compared over time and domain.

There have been over twenty-five annual surveys in the series. Since 1995, the surveys have included children who live in households selected for the survey; children aged 2-15 were included from 1995, and infants under two years old were added in 2001. The data are weighted relative to the size of each group of the population making the results comparable over the time series

The core topics covered by the survey include general health, fruit and vegetable consumption, height and weight, obesity and overweight, alcohol consumption and smoking. Trend tables present data for key measures for the years in which they were collected to make comparisons over time more accessible. The number of years of data available varies; from a few years for newer topics such as well-being, to others such as general health, smoking status, height, weight and body mass index, for which data were first collected in 1993 or 1995. The Health Survey for England content page includes information about which topics were included each year of the survey from 1993 to 2021.

Owing to the Covid-19 pandemic, in 2021, the approach differed from previous years. This included a change in mode, from face-to-face interviewer visits to remote telephone and a small proportion of video interviews, to limit contact between participants and interviewers. For January to March 2021 the survey was opt in and participants had to contact NatCen to schedule a survey interview. From April onwards the survey moved back to doorstep recruitment, but survey interviews were then arranged for over the telephone at a later date rather than face to face. The survey contains a self-completion element: during the face-to-face interview participants complete the self-completions during the interview, however for 2021 these were asked to be completed after the interview and posted back, reminder letters were sent. This led to lower numbers of response for the self-completion elements of the survey. More details are within the Methods Report

In previous years, participants would have had their height and weight measured during the face-to-face interview. In 2021, this was replaced with using self-reported height and weight to estimate overweight and obesity prevalence. A methodology study using HSE data from 2011 to 2016 developed a set of prediction equations that adjusted self-reported values of height and weight so that they more accurately predicted measured values of height and weight. The difference in methodology  should be considered when reviewing trend data. More information about the impact of changing how height, weight and body mass index were measured is available at Methodological changes - NHS Digital and within the Methods Report.


Trade-offs between output quality components

This dimension describes the extent to which different aspects of quality are balanced against each other.

Changes were made to the 2021 survey to allow for data collection to be carried out in a timely fashion after data collection for the 2020 survey had to be stopped in March 2020 due to the Covid-19 pandemic (with no subsequent annual publication). The change from face-to-face to telephone and video interview has potential to affect the recruited sample and also to impact on how people answer.

It is also possible that some question topics in HSE (e.g. smoking, drinking and fruit and vegetable consumption) may be susceptible to social desirability bias, where the individual is tempted to give an answer which is more socially acceptable. Respondents are assured that their answers will be kept private to reduce this temptation and more sensitive themes are asked via self completion to allow more privacy when answering.


Assessment of user needs and perceptions

This dimension covers the processes for finding out about users and uses and their views on the statistical products.

From our engagement with customers, we know that there are many users of these statistics. They are used by the Department of Health and Social Care, Office for Health Improvement and Disparities, NHS England, Local Government, charities, academics, professional groups, the public and the media. Uses of the data include:

  • Informing, monitoring and evaluating policy;
  • Monitoring changes in health or health related behaviours e.g. smoking;
  • Comparing local indicators with national figures;
  • Informing the planning of services;
  • Writing media articles.
  • Health and social research

NHS Digital tries to engage with users of these statistics to gain a better understanding of the uses and users and to ensure these statistics remain relevant and useful. We capture information on the number of unique page views the reports and tables receive and this survey is one of our most frequently viewed publications.

The survey questionnaire and content of the report is discussed and agreed with a steering group which contains representatives from NHS Digital, Department of Health and Social Care, Office for Health Improvement and Disparities, NHS England, academia, Local Government Public Health and other government departments as well as the contractor carrying out the survey.

NHS Digital is keen to gain a better understanding of the users of this publication and of their needs; feedback is welcome and may be sent to [email protected] (please include ‘Health Survey for England’ in the subject line).


Performance, cost and respondent burden

This dimension describes the effectiveness, efficiency and economy of the statistical output.

Data for the Health Survey for England (HSE) 2021 were collected from the population living in private households in England.

As in previous years, the HSE 2021 used a stratified random probability sample of households. The sample comprised of 9,774 addresses in 543 postcode sectors for the core sample, and 3,024 addresses in 168 postcode samples for the reserve sample. Adults and children were interviewed in households identified at the selected addresses. To limit the burden of responding for parents, no more than four children in each household were selected at random: up to two children aged between 0 and 12, and up to two aged between 13 and 15.

Data collection comprised a telephone or video interview. Participants in the interview were sent a paper questionnaire with additional questions to complete and return by post. A proportion (89%) of participating households were invited to have a visit from a specially trained nurse. The nurse visit included additional questions, measurements, collection of blood samples from adults aged 16 and over, urine samples from adults aged 35 and over, and saliva samples from adults and children aged 4 and over.

A household response rate of 32% was achieved. In total, 5,880 adults and 1,240 children were interviewed, including 1,705 adults and 250 children who had a nurse visit.


Confidentiality, transparency and security

The procedures and policy used to ensure sound confidentiality, security and transparent practices. 

The data contained in this publication are National Statistics. The Code of Practice for Statistics is adhered to from collecting the data to publishing.

No personal/individual level information is contained in the report. Information is presented at a high level of aggregation. As for all NHS Digital publications the risk of disclosing an individual’s identity in this publication series has been assessed and the data are published in line with a Disclosure Control Method for the dataset.

Please see links below to relevant NHS Digital policies:

Statistical Governance Policy

https://digital.nhs.uk/data-and-information/find-data-and-publications/statement-of-administrative-sources/a-z-of-nhs-digital-official-and-national-statistics-publications#user-documents

Freedom of Information Process

https://digital.nhs.uk/about-nhs-digital/contact-us/freedom-of-information

A Guide to Confidentiality in Health and Social Care

https://digital.nhs.uk/about-nhs-digital/our-work/keeping-patient-data-safe

Privacy and Data Protection

https://digital.nhs.uk/about-nhs-digital/privacy-and-cookies


Last edited: 16 May 2023 9:31 am