The Global Burden of Disease England Technical Guide

The Global Burden of DiseaseEngland

Technical Guide

IntroductionThis document has been designed to answers queries or questions related to the Global Burden of Disease: England Study and Visualisations.

The England Burden of Disease study is an interactive way to access information about diseases and the attributable relationship with risk factors. The data is modelled using Global Burden of Disease (GBD) methodology and the process ensures that all data inputs and outputs are quality assured and modelled in a systematic and consistent way. All the data and outputs are freely available for interrogation and further investigation by anyone.

The England Burden of Disease study is a an output of the international Global Burden of Disease study undertaken by Institute of Health Metrics and Evaluation (IHME) in Seattle US.

2 The Global Burden of Disease: England - Technical Guide

InputsData Sources: the study uses a wide range of data sources, including administrative and clinical databases, surveys and published study results. Web table 2 in the England GBD 2013 paper shows the complete list of sources used in modelling GBD England estimates.

Data Refresh: data is refreshed and added to the model constantly as it becomes available. The paper, ‘Changes in health in England with analysis by English region and level of deprivation: findings of the Global Burden of Disease Study 2013’ used the best available evidence at the time the paper was published (15 September 2015).

The data shown in the visualisation tool are updated intermittently and give a more accurate reflection of the most current data for England and its regions.


Process: GBD outputsThe GBD approach uses multiple modelling strategies to produce the different metrics of the burden of disease, which are available consistently for all countries participating in the study (188 in Spring 2015). The main burden metrics are:

• deaths• healthy life expectancy• years of life lost (YLL)• years lived with disability (YLD)• disability adjusted life years (DALYs)

For England and its sub-national areas, these main metrics are also available from the GBD models (excluding healthy life expectancy). As well as these outputs, the GBD also provides risk factors attributable to deaths, YLL, YLD and DALYs.

All of the metrics are available by gender and different age-groupings, geographical location and level of deprivation. The latter are grouped into 45 sub-regions (nine regions by five levels of deprivation).


GBD analytical principlesThe GBD protocol (http://www.healthdata.org/gbd/about/protocol) lists the principles and assumptions used in the construction of its outputs. A summary of some of the main analytical principles are listed below:

• the GBD produces estimates for a mutually exclusive and collectively exhaustive set of disease and injury causes. They also try to convey to users the strength of the evidence for each quantity through the reporting of uncertainty intervals (UI) for all estimates

• the GBD estimates all quantities of interest in all time periods. An uncertain estimate is believed to be preferable to no estimate even when data are sparse or not available

• the GBD synthesises all the appropriate data using statistical methods designed to handle both sampling and non-sampling error

• the GBD methods also allow the use of covariates to improve predictions for where data are sparse by borrowing strength across time or geography

• all estimates should be generated with 1,000 (or more) draws from the posterior distribution of the quantity of interest


http://www.healthdata.org/gbd/about/protocol

Process outlineThere are 22 key components outlined in the estimation process for GBD 2013[1]. A brief overview of these processes is provided below, but a more comprehensive understanding of the methodological process should be taken from the list of publications included at the end of this slide set.

The flowchart in figure 1 (next slide) shows the key components in the construction of the GBD 2013 estimation process.


[1] Protocol for the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD). Issued March 2015. Institute for Health Metrics and Evaluation

Figure 1: outline process and components


Process outline descriptionCovariates database

GBD uses covariates to inform the estimation process in all models in the GBD Study, by including these in the statistical models. A complete time series of covariates are calculated to inform this process of burden estimation.

Death estimates

Child and adult mortality by age-group are estimated using data sources such as vital and sample registration systems, censuses, and household surveys. Sources will differ across countries. For England, mortality from the vital registration system from the Office for National Statistics (ONS) is used. The models used to calculate final mortality estimates will have very little impact on the ONS published England mortality data (by gender and age), as the vital registration system in England (and UK) has complete population coverage.


Years of life lost and deaths by causeYears lost due to premature death (YLLs) and deaths from different cause groups in England are calculated using source data from vital registration medical certification of causes of death, as published from the underlying cause of death from the Office for National Statistics. Other countries may use other single or multiple sources, such as verbal autopsies, where medical certification of causes of death is lacking within their population.

For England, a proportion of causes of death in the vital statistics database are re-coded to other causes in line with GBD algorithms identifying non-specific, ill-defined or other causes not considered underlying causes. Once re-coding is complete, the modelling of cause of death by gender for all age-groups is undertaken to produce final estimates. Multiple modelling strategies are used for different conditions, of which the largest method (155 causes) is Cause of Death Ensemble (CODEm) modelling.


Years of life lost and deaths by cause (continued)

The final GBD estimates will differ from the re-coded data (as above) where vital statistics on death data is sparse, such as rarer causes or within specific ages. The GBD process also produce estimates for some cause groups where ONS mortality coding is not available.


Years lived with disability estimatesYears lived with disability (YLD) are estimated from disease and injury sequelae prevalence estimates combined with matched ‘health state’ disability weights.

Prevalence estimates uses sources such as cancer registries, data from outpatient and inpatient facilities, and direct measurements of hearing, vision and lung function testing. For England, this includes multiple sources, including national surveys, the national cancer registration system, hospital episode statistics and multiple published studies on various disease and condition topics.

The modelling of prevalence adjusts for potential data source biases using standard disease case definitions globally. Multiple modelling approaches are used depending on specific sequelae, with the most common method using the Bayesian meta-regression tool DISMOD II MR.


YLD estimates (continued)Disability weights are produced for different health states from international lay-person responses to a GBD administered health state questionnaire. Disability weights are not country-specific and assumed to have the same response pattern in all cultures and life phases. Each health state is mapped to disease or injury sequelae.

Disability weights for each sequelae are multiplied by disease sequelae to gain disease sequelae YLDs. Each of these disease YLDs are then summed in the YLD cause list.

A co-morbidity simulation process models the multi-morbidity of different sequelae. YLDs for co-morbid sequelae are adjusted to take into account this multi-morbidity effect.

Although this process above is applied to England and regional results, YLDs for deprivation areas in England have been approximated from regional level results, so do not use the full modelling process.


Risk factor estimatesThe amount of premature death and disability in GBD 2013 by cause is attributed to 79 different risk factors (grouped into three risk categories) using data on exposure to, and the effects of the different risk factors.

Attributable burden is estimated by comparing observed health outcomes to those that would have been observed if an alternative (theoretical minimum) level exposure had occurred in the past. Assessments are undertaken in risk-outcome pairs in a standardised way in order to ensure comparability of the results across risks, population and time.

In England, data on exposure is taken from multiple sources from surveys, administrative sources and published studies


GBD publications with methodologyMurray CJ, Ezzati M, Flaxman AD, et al. GBD 2010: design, definitions, and metrics. Lancet 2012; 380: 2063–66.

Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012; 380: 2224–60.

Lozano R, Naghavi M, Foreman K, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012; 380: 2095–128.

Murray CJL, Vos T, Lozano R, et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012; 380: 2197–223.


GBD publications with methodologySalomon JA, Vos T, Hogan DR, et al. Common values in assessing health outcomes from disease and injury: disability weights measurement study for the Global Burden of Disease Study 2010. Lancet 2012; 380: 2129–43.

Vos T, Flaxman AD, Naghavi M, et al. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012; 380: 2163–96.

Naghavi M, Murray CJL, Lopez AD. GBD 2013 Mortality and Causes of Death Collaborators. Global, regional and national levels of age-specific mortality and 240 causes of death, 1990-2013: A systematic analysis for the Global Burden of Disease Study 2013. Lancet 2015;385:117–71.

Vos T, Barber RM, Bell B, Bertozzi-Villa A, Biryukov S, Bolliger I, et al. Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 2015


GBD publications with methodologyMurray CJL. GBD 2013 Risk Factor Collaborators. Global, regional, and national comparative risk assessment of 76 behavioural, environmental, occupational, and metabolic risks or clusters of risks in 188 countries 1990-2013: a systematic analysis for the Global Burden. Lancet 2015.

Protocol for the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD). Issued March 2015. Institute for Health Metrics and Evaluation


Caveats and limitationsAs with all modelled estimates a number of limitations and caveats exist. The estimates produced will not compare directly to reported statistics within England, where these are available because none of the estimates are directly reported from England data sources, as all estimates are constructed using multiple GBD methodologies.

England disease prevalence data used to create non-fatal condition estimates (YLD) draws heavily on published literature sources of UK data, so estimates may not always be representative of the smaller geographic areas in England and thus may underestimate morbidity patterns. Although England has many database sources to inform disease prevalence including administrative systems, disease registries, clinical audit programmes and other surveillance hubs, only some of these data sources were available for use at time of data collection to inform the GBD modelling.


Outputs (current)

The current England Burden of Diseases study allows an examination of: the main risk factors, broader co-variates, outcomes, and their relationship across 45 sub-national areas (nine regions by five deprivation levels).

The data allows the description and initial analysis of variation of population outcomes in England, and their comparison to European and non-European countries.


Outputs (future)Improving estimates for non-fatal estimates and YLD:

Currently non-fatal estimates for England and sub-national areas are limited by the data sources available. Further work is being developed on the interrogation of electronic health records in primary care to enhance these estimates.

Granularity of output:

PHE and the Institute of Health Metrics and Evaluation (IHME) at the University of Washington are working together to ascertain if the methodology can produce outputs to a more local level within England.

Predictive modelling for future estimates:

One of the next steps for IHME is to provide future predictions of disease burden at national level.


Access to source dataAll data sources used in the study are cited in the supplementary appendix, web table 2, data provided by PHE are in the next slide.

All data sent to IHME by PHE are listed on the .gov.uk website and links to the original sources can be found here.

Some of the data used to create the visualisations on the IHME website can also be downloaded by clicking on the links provided on the relevant page.

All data used is in aggregate format and is available on the IHME website via the .gov.uk website for download and use by anyone.



Description UK data sourced Region Years Age Sex IMD

Mortality and

Patient Data

Live births, all-cause mortality, mortality by cause morbidity data & population denominators

Office of National statistics (ONS)

Yes Yes Yes Yes No

Cancer Incidence Cancer registries Yes Yes Yes Yes Yes

Renal replacement therapy UK Renal registry Yes Yes Yes Yes No

Hospital treatment by deprivation groups Hospital Episode Statistics (HES)

Yes Yes Yes Yes Yes

Common psychiatric conditions Adult Psychiatric Morbidity Survey

Yes Yes Yes Yes No

Dementia estimates Cognitive Ageing and Function Study

UK only Yes Yes No Yes

Programme Budgeting NHS England Yes Yes No No No

GP patient survey GP patient survey for England Yes Yes Yes Yes Yes

Covariates

Education (years per capita) Labour Force Survey Yes Yes No No No

Gross domestic product per capita Quarterly National Accounts Yes Yes No No No

Litres of alcohol per adult HMRC & General Lifestyle Survey

Yes Yes No No No

Measles vaccination coverage & DTP3 coverage Public Health England (PHE) Yes Yes No No No

Smoking prevalence & Cigarettes consumed per adult Health Survey for England (HSE)

Yes Yes Yes Yes Yes

Mean BMI, total cholesterol & systolic blood pressure HSE Yes Yes Yes Yes Yes

Diabetes prevalence HSE/Quality Outcomes framework (QOF)

Yes Yes Yes Yes Yes

Mean estimated salt intake (g/day) National Diet and Nutrition Survey (NDNS)

Yes Yes Yes Yes Yes

Kcal & grams of nuts and seeds/ fruit/ whole grains/ vegetables/ red meat/ milk/ sugary drinks consumed per capita per day

NDNS Yes Yes No Yes YES

Total Kcal & grams consumed per capita per day NDNS Yes Yes No No No

Population density ONS Yes Yes No No No

Air pollution GOV.UK UK Only Yes No No No

Number of 2 & 4 wheeled vehicles per capita GOV.UK Yes Yes No No No


About Public Health EnglandPublic Health England exists to protect and improve the nation's health and wellbeing, and reduce health inequalities. It does this through world-class science, knowledge and intelligence, advocacy, partnerships and the delivery of specialist public health services. PHE is an operationally autonomous executive agency of the Department of Health.

To contact the Global Burden of Disease study in Public Health England use: [email protected]

Access to GBD Visualisation tool is: http://vizhub.healthdata.org/gbd-compare/england

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Published September 2015PHE publications gateway number: 2015301

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The Global Burden of Disease England Technical Guide