1. Methodology background


 National Statistic   
 Frequency  Annual
 How compiled  Administrative data, survey data
 Geographic coverage  UK, England, Wales, Scotland, Northern Ireland
 Last revised  25 October 2017

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2. Executive summary

We previously published Life expectancy, National health and Disability-free life expectancy, Healthy life expectancy for local areas in England and Disability-free life expectancy for local areas in separate bulletins. These have now been streamlined into one bulletin called Health state life expectancies.

Life expectancy and Health state life expectancies are important high-level measures of a population’s health status.

Period life expectancy (LE) at a given age for an area is the average number of years a person would live, if he or she experienced the particular area’s age-specific mortality rates for that time period throughout his or her life.

Health expectancies (HEs) are extensions of LE that combine mortality data with both general and functional health status data to produce estimates of the span of life that a person can expect to live in “Very good” or “Good” health –healthy life expectancy (HLE), or without a limiting long-standing illness or disability – disability-free life expectancy (DFLE).

This partitioning of length of life into periods spent in various health states provide a quality dimension to LE. These metrics provide an informative summary measure of the health status of the population, which provides a context to changing patterns in life span.

The publication provides figures for males and females at national, regional and local level. The figures presented are 3-year rolling averages to ensure they are sufficiently robust at all geographic levels.

This report contains the following sections:

  • Output quality

  • About the output

  • How the output is created

  • Validation and quality assurance

  • Concepts and definitions

  • Other information, relating to quality trade-offs and user needs

  • Sources for further information or advice

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3. Output quality

This report provides a range of information that describes the quality of the data and details any points that should be noted when using the output.

We have developed Guidelines for Measuring Statistical Quality; these are based upon the five European Statistical System (ESS) Quality Dimensions. This report addresses these quality dimensions and other important quality characteristics, which are:

  • relevance

  • timeliness and punctuality

  • coherence and comparability

  • accuracy

  • output quality trade-offs

  • assessment of user needs and perceptions

  • accessibility and clarity

More information is provided about these quality dimensions in the following sections.

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4. About the output

Relevance

(The degree to which statistical outputs meet users’ needs.)

Our statistics Health state life expectancies (HLE) output has two components, each of which has different population coverage:

  • estimates of period life expectancy (LE) cover the UK and constituent countries, and for England regions, counties and local authority districts, and for Wales’s unitary authorities

  • estimates of health state life expectancy cover the UK and constituent countries, and for England, regions, upper tier local authorities and clusters of lower layer super output areas (LSOAs) grouped according to their area deprivation quintile or decile as measured by the Index of Multiple Deprivation (IMD)

Figures are not calculated for City of London or Isles of Scilly because the numbers of deaths are too small to produce statistically robust estimates.

On 1 April 2009, there was a reorganisation of local government in England, which created nine new unitary authorities (based on the merging of 37 local authorities). Life expectancy figures based on both the old and new boundaries are available.

Figures are published annually in October for the preceding 3-year period, following the release of death registrations data and mid-year population estimates (usually both available by the end of August of the publication year).

Figures are available for life expectancy at birth for 1991 to 1993 onwards (apart from counties, which are available for 2000 to 2002 onwards) and for life expectancy at age 65 for 2000 to 2002 onwards (apart from areas in Scotland, which are available for 2004 to 2006 onwards).

Health state life expectancies at UK and constituent country level data are available back to 2000 to 2002. These estimates combine data from the General Lifestyle Survey (GLF) (formerly known as the General Household Survey (GHS)) for Great Britain and from the Continuous Household Survey (CHS) for Northern Ireland and Health Survey Northern Ireland (HSNI) from 2010.

Survey data are combined with interim life tables and mid-year population estimates to give a measure of the quality of remaining years of life by age group, sex and area.

Data for Great Britain and England are available dating back to 1980 to 1982, although there are gaps for the years 1995 to 1997, 1997 to 1999 and 1999 to 2001 due to suspension of the GHS in 1997 and 1999.

In 2005, the GHS underwent two changes. The first was a change in survey design, from a purely cross-sectional survey to one with a longitudinal rotating panel design, becoming the GLF. There was a consequent loss of precision, and possibly accuracy in our estimates of healthy life expectancy (HLE) and disability-free life expectancy (DFLE), evidenced by a widening in the 95% confidence intervals (CI) surrounding each estimate. This change, along with an improvement in the method to account for sample selection, was reported in Health Statistics Quarterly (HSQ) and (Smith et al., 2010b). Also, the general health survey question used in the calculation of HLE was harmonised to the European Union Statistics on Income and Living Conditions (EU-SILC) Minimum European Health Module question containing five health state categories. This change in the data input and the derived definition of “Good” general health led to a substantial fall in the absolute value of HLE, which was reported in HSQ (Smith and White, 2009). A simulated time series of HLE was developed to provide users with a consistent synthetic series between 2000 to 2002 and 2004 to 2006 leading to the adoption of the harmonised measure of HLE in 2005 to 2007. Our HLE is now broadly comparable with that of other EU member states and has the added advantage of consistency with data available from the 2011 Census.

There is a time series of subnational estimates of healthy life expectancies from 2009 to 2011. Subnational estimates have been produced from 2006 to 2008 for DFLE. Both use a 3-year aggregated and reweighted version of the Annual Population Survey (APS).

Inequality in healthy life expectancy at birth for England is also measured using the APS: This output quantifies the socioeconomic gap between the least and most deprived populations.

LSOAs are grouped into deciles based on their IMD 2010 score, the scores of which have been adjusted to reflect LSOA boundary changes in 2011. The responsibility for producing these adjusted deprivation scores lies purely with Public Health England (PHE) – the figures have neither been quality-assured nor endorsed by the Department for Communities and Local Government (DCLG), but have been used in Public Health Outcomes Framework indicators. Further details on how the scores were adjusted is available. The prevalence of “Good” and “Not good” general health are computed for each decile using APS data starting with the period 2009 to 2011 and annually moving forward. These data are combined with mortality data to compute expectation of life for each decile in “Good” general health; the inequality is measured using the Slope Index of Inequality.

Life expectancy provides users with an indicator of health, which can be used to inform policy, planning and research in both public and private sectors in areas such as health, population, pensions and insurance. Main users include the Department of Health, primary care organisations, public health observatories, local authorities, and private pensions and insurance companies.

Life expectancy figures are used at regional and local levels to focus on health monitoring and planning in specific areas. They are also published as part of the Regional Health Profiles, which are produced by Public Health England (PHE) . The profiles comprise an important package of indicators, which are designed to support action by local governments and primary care trusts to tackle health inequalities and improve people’s health. Life expectancy figures are also presented for local authority areas in PHEs Public Health Outcomes Framework.

In the private sector, life expectancy figures are used by pensions and insurance companies for planning their financial services.

Our HE statistics are reported in a number of our other publications such as National Well-being – Health and Pension trends. Main external users of our health expectancy statistics include:

Timeliness and punctuality

(Timeliness refers to the lapse of time between publication and the period to which the data refer. Punctuality refers to the gap between planned and actual publication dates.)

The annual release of life expectancy figures is announced on the GOV.UK release calendar 12 months in advance. Results are published in October or November each year (10 or 11 months after the end of the reference period), following the release of annual death registrations data and mid-year population estimates for the previous year (usually by the end of August). Results are produced on a 3-year rolling average basis, to provide large enough numbers to ensure that the figures are sufficiently robust. Life expectancy figures are released at the same time every year and have always been punctual.

Previously, there has been a delay in producing the Health state life expectancies. These will now be produced at the same time as the Life expectancies and will be released in October or November. For more details on related releases, the GOV.UK release calendar provides 12 months advance notice of release dates. If there are any changes to the pre-announced release schedule, public attention will be drawn to the change and the reasons for the change will be explained fully at the same time, as set out in the Code of Practice for Official Statistics.

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5. How the output is created

To calculate life expectancy, abridged life tables are constructed using standard methods, through procedures that have been extensively tested. Separate tables are constructed for males and females. They are created using numbers of deaths registered in calendar years and mid-year population estimates. Results and 95% confidence intervals are calculated using an internal Stata programme and checked using a life table template in MS Excel. The template provides a detailed description of the standard methods and notation associated with the calculation of life expectancy.

Our statistics health expectancy (HE) outputs all use the same core methodology, the Sullivan Method. Briefly, this method combines survey data, for example, the Annual Population Survey (APS) with life expectancy to calculate the number of remaining years, at a particular age, in which an individual can expect to live in a given state of health. We use the following definitions of health to calculate both healthy life expectancy (HLE) and disability-free life expectancy (DFLE).

HLE is defined as the number of remaining years that an individual can expect to live in “Very good” or “Good” general health. Rates of “Very good” and “Good” general health by sex and 5-year age band are captured from the following survey general health question on the APS:

  • How is your health in general; would you say it was…
    Very good?
    Good?
    Fair?
    Bad?
    Very bad?

DFLE is defined as the number of remaining years that an individual can expect to live without a limiting long-standing illness. Rates of limiting long-standing illness by sex and 5-year age band are captured from the following survey questions asked in the APS:

  • Do you have any health problems or disabilities that you expect will last for more than a year? Yes/No

If “Yes” the respondent is then asked:

  • Do these health problems or disabilities, when taken singly or together, substantially limit your ability to carry out normal day-to-day activities? If you are receiving medication or treatment, please consider what the situation would be without the medication or treatment. Yes/No
LFS questions (before April 2013)
Harmonised questions (from April 2013)
LNGLIM

Do you have any health problems or disabilities that you expect will last for more than a year?

1 Yes
2 No
LNGLST (replacing LNGLIM)

Do you have any physical or mental health conditions or illnesses lasting or expected to last 12 months or more?

1 Yes
2 No
HEALIM

Do these health problems or disabilities, when taken singly or together, substantially limit your ability to carry out normal day-to-day activities?

1 Yes
2 No
LIMACT (replacing HEALIM)

Does your condition or illness/do any of your conditions or illnesses reduce your ability to carry out day-to-day activities?

1 Yes, a lot
2 Yes, a little
3 Not at all


Survey data are weighted to match age, sex and regional profiles with mid-year population estimate projections. This calibration process ensures consistency between survey and population estimates and, additionally, compensates for potential bias that might arise from differential non- response among different sub-groups in the sample selected for the survey.

Data for the APS are weighted by age and sex and are also adjusted to account for sample selection and multi-household addresses. The cross-sectional elements of the APS are further weighted for non-response while the longitudinal elements of these surveys are weighted for attrition after first interview. Further information on survey data weighting is given in the Integrated Household Survey User Guide.

The APS is a continuous survey of households in the UK, which is produced quarterly and contains annual data. Each dataset (known as a quarterly rolling annual dataset) consists of wave 1 and 5 of the quarterly Labour Force Survey (LFS) and additional boost cases in England, Wales and Scotland, which are added to ensure that a sufficient number of interviews are conducted with economically active people in each local education authority area.

Each APS dataset contains approximately 170,000 households and 320,000 individuals. The primary purpose of the APS is to provide estimates for labour market and socio-economic analyses at subnational level and the APS is the recommended source of statistical information for analysis at unitary authority and local authority district level.

Although the design of the APS has a longitudinal element, the aggregated 3-year period used in the subnational analyses of DFLE and HLE ensures the study population used excludes duplicate survey responders. The APS is intended to be representative of subnational populations including regions, upper and lower tier local authorities. The following chart shows how the study population for the subnational DFLE and HLE estimates are constructed from distinct waves of the LFS and APS boost.

From 2016 and the publication updated to include 2013 to 2015 estimates, all estimates are produced from the APS. This includes the national and subnational health state life expectancies as well as the HLE by Index of Multiple Deprivation (IMD).

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6. Validation and quality assurance

Accuracy

(The degree of closeness between an estimate and the true value.)

All figures are period life expectancies. Period expectation of life at a given age for an area in a given time period is an estimate of the average number of years a person of that age would survive if he or she experienced the particular area’s age-specific mortality rates for that time period throughout the rest of his or her life. The figure reflects mortality among those living in the area in each time period, rather than mortality among those born in each area. It is not therefore the number of years a person in the area in each time period could actually expect to live, both because the death rates of the area are likely to change in the future and because many of those in the area may live elsewhere for at least some part of their lives.

The subnational life expectancy calculations use abridged life tables (based on grouping ages) rather than complete ones (based on single year of age). Through procedures that have been extensively tested, these abridged tables are more suitable than complete life tables (based on single year of age) for calculating subnational life expectancy due to small numbers of deaths by single year of age, particularly among younger ages and in smaller local authorities. They are created using numbers of deaths registered in calendar years and mid-year population estimates. Life expectancy figures are calculated as 3-year rolling averages to provide large enough numbers to ensure that the results are sufficiently robust.

A template, which shows how abridged life tables are calculated is available.

Before the annual release, life expectancy figures for local and unitary authorities are calculated as part of the process for quality assuring mid-year population estimates for England and Wales. The analyses highlight potential outliers in the distribution of new life expectancy estimates and compare results with those calculated for the previous period.

For information about the underlying mortality and population data used for life expectancy calculations, please see the following links:

Health expectancies are secondary analyses of published survey, mortality and mid-year population estimates. As such, the data has already been subject to rigorous quality control procedures. Our health expectancies are calculated subject to a rigorous documented quality control procedure. Calculations are performed independently by two members of our Health Analysis team using STATA®, SAS® and Excel. Inconsistency and missing data checks are initially performed on the survey data. An example of an inconsistency would be where a person is reported not to have a long-standing illness but at the same time is recorded as having a limitation resulting from a long-standing illness. Missing data and inconsistencies are deleted from the final survey dataset.

Life and health expectancies estimates are published with 95% confidence intervals (CIs) to allow the user to judge their precision and identify significant differences between data points (area, sex, age and time period). Health expectancies(HE) CI calculations are calculated from weighted prevalence and unweighted survey counts, outlined by the Sullivan method and include an adjustment to improve the accuracy of the standard error of HEs by accounting for the multi-stage sampling design effects of the survey sources. While more formalised and accurate methods of significance testing are available, the non-overlapping CI method is used because it is both simple to calculate and easily understood. However, a formal statistical test of the difference in health expectancies from England is calculated and where such a test shows the difference is significant, this is identified in datasets.

Coherence and comparability

(Coherence is the degree to which data that are 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, for example, geographic level.)

Life expectancy and health expectancies are an indicator of mortality and population health, which takes into account differences in the age structures of populations. Results for local areas can therefore be meaningfully compared, as can results for males and females.

All figures for life expectancy at birth and at age 65 for 1991 to 1993 onwards were calculated using the same method and are therefore comparable. Results for 1991 to 1993 onwards are all based on the latest population estimates available.

Individual deaths are assigned to geographical areas by linking the postcode of usual residence of the deceased to the latest version of the National Statistics Postcode Directory (NSPD). This means that figures for each 3-year period may be based on slightly different boundaries, where, for example, postcodes are re-allocated from one area into another. The impact on life expectancy results is minimal and comparability over time is not therefore affected.

Deaths of non-residents are excluded from local area life expectancy estimates, since they cannot be assigned to a geographical area. However, when life expectancy estimates are calculated for England and Wales as a whole, non-residents are included as they do not need to be assigned to a specific geographical area.

The national interim life tables provide the definitive life expectancy figures for the UK and constituent countries. These are calculated using complete life tables (based on single year of age) and should be used when comparing results with other countries.

To provide comparisons for regional and local area figures, national life expectancy results are also produced within this output using the same method as the subnational results, with abridged life tables in which death and population data are aggregated into age groups. Therefore, the two sets of national figures may differ very slightly (usually around 0.1 years).

Figures for England will also differ slightly from the national interim life table results because of a difference in the handling of deaths of non-residents. For this output, the deaths of non-residents are included in the mortality figures for England and Wales, but are excluded from the figures for England and Wales separately. However, for the national interim life tables, the deaths of non- residents in England and Wales are included in the mortality data for England, but not in Wales.

Scotland produces estimates of healthy life expectancy (HLE), Scottish healthy life expectancy (SHLE), that differ slightly from our estimates of HLE. This is because different survey sources are used; SHLE is based on the Scottish Health Survey.

There are a number of issues that arise when trying to compare health expectancies (HEs) derived from different sources or methods. In general HEs are sensitive to:

  • measurement instruments used to collect the prevalence of health status, as the concept or definition of health may vary by survey or country

  • the survey mode, for example face-to-face interview, telephone interviews or postal or online surveys

  • exclusion or inclusion of institutionalised persons

Differences between HEs for different countries can often be explained by differences in these issues. It is therefore important that they are taken into account before attempting comparisons between countries.

HEs are calculated in other European member states and the issues described in this sectionhave also been highlighted in a comprehensive review (Bone et al., 1995).

National estimates of disability-free life expectancy (DFLE) for Great Britain and England between 1980 to 1982 and 2008 to 2010 are broadly comparable, as are figures for the UK, Wales, Scotland and Northern Ireland between 2000 to 2002 and the latest period. From 2005 to 2007, our estimates of HLE were based upon the EU-SILC general health question and so estimates after this date are not directly comparable with estimates prior to this date. A synthetic time series between 2000 to 2002 and 2004 to 2006 showing revised estimates of HLE for the UK and constituent countries based on the EU-SILC general health question are included in the associated national datasets.From 2016, a new UK HLE and DFLE time series was published, which has estimates from 2009 to 2011 based on the Annual Population Survey. This is not comparable with previous estimates.

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7. Concepts and definitions

(Concepts and definitions describe the legislation governing the output and a description of the classifications used in the output.)

Expectations of life can be calculated in two ways: period life expectancy (as used in this output) and cohort life expectancy. Cohort life expectancies are calculated using age-specific mortality rates, which allow for known or projected changes in mortality in later years and are therefore regarded as a more appropriate measure of how long a person of a given age would be expected to live, on average, than period life expectancy. For example, period life expectancy at age 65 in 2000 would be worked out using the mortality rate for age 65 in 2000, for age 66 in 2000, for age 67 in 2000, and so on. Cohort life expectancy at age 65 in 2000 would be worked out using the mortality rate for age 65 in 2000, for age 66 in 2001, for age 67 in 2002, and so on.

Period life expectancies are a useful measure of mortality rates actually experienced over a given period and, for past years, provide an objective means of comparison of the trends in mortality over time, between areas of a country and with other countries. Official life tables in the UK and in other countries, which relate to past years, are generally period life tables for these reasons. Cohort life expectancies, even for past years, usually require projected mortality rates based on a set of assumptions for their calculation and so, in such cases, involve an element of subjectivity. More information on the differences between period and cohort life expectancies is available.

Healthy life expectancy is the period of time that an individual can expect to live in “Vvery good” or “Good” health. This self-reported health state is taken from survey data in response to a general health question.

Disability-free life expectancy is the period of time that an individual can expect to live without a long-standing illness that limits normal daily activities. This self-reported health state is taken from survey data in response to questions relating to long-standing illness and activity limitation resulting from it.

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8. Other information

Output quality trade-offs

(Trade-offs are the extent to which different dimensions of quality are balanced against each other.)

Life expectancy figures are not routinely calculated by us for areas smaller than local authorities due to small numbers of deaths and populations. More information can be found in a report titled Life expectancy at birth: methodological options for small populations. However, for 5-year periods centred on the census year, we have produced Health state life expectancies for Middle Layer Super Output Areas.

Assessment of user needs and perceptions

(The processes for finding out about use and users, and their views on the statistical products. are maintained with a range of users including those from government and academics.)

Understanding user needs is important to us, and we invite feedback from users regarding both the statistical bulletin and this Quality and Methodology Information report. Face-to-face meetings and email and telephone correspondence is maintained with a range of users including government users, academics, students and interested individuals.

A user consultation to review health expectancy statistics we produce took place in 2008 and the response to the review is available.

Users were also consulted as part of the UK Statistics Authority assessment of compliance with the Code of Practice for Official Statistics.

The Health Analysis Team maintains a list of known users including which statistical outputs they use and how they use them. All known users will be invited to participate in any future consultation.

Feedback is also received through our regular attendance at Royal Statistical Society Health Statistics User Group meetings and academic conferences.

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9. Sources for further information or advice

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 release details, illustrations and accompanying advice.)

Our recommended format for accessible content is a combination of HTML web pages for narrative, charts and graphs, with data being provided in usable formats such as CSV and Excel. Our website also offers users the option to download the narrative in PDF format. In some instances other software may be used, or may be available on request. Available formats for content published on our website but not produced by us, or referenced on our website but stored elsewhere, may vary. For further information please refer to the contact details at the beginning of this report.

For information regarding conditions of access to data, please refer to the following links:

In addition to this Quality and Methodology Information, basic quality information relevant to each release is available in the quality and methodology section of the relevant statistical bulletin.

We welcome your feedback. If you have any comments or questions about the statistical bulletin or this Quality and Methodology Information, please get in touch using the email address provided.

Useful links

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Contact details for this Methodology