Reporting guidelines for burden of disease studies: why and how?

Background

The Disability Adjusted Life Year (DALY) is a frequently used metric to assess burden of disease (BoD). Many independent BoD studies have been performed across Europe, showing wide variations and inconsistencies in the application and reporting of DALY specific methods. The European Burden of Disease Network (burden-eu) aims to develop guidelines for reporting DALY calculation studies which may enhance transparency and comparability of BoD estimates across Europe and beyond.

Methods

A burden-eu working group of experts generated a list of potential reporting items based on existing literature, guidance for developing guidelines and consultations with BoD experts. To pilot the drafted product, we asked BoD experts and non-experts to apply it to existing BoD studies. We received feedback and we revised the guidelines accordingly.

Results

The guide for DALY calculation studies comprises about 25 items that should be reported in BoD studies. We included information about the study setting, data input sources including methods for data corrections, DALY-specific methods (e.g., YLL life table, YLD approach, disability weights etc), data analyses, and data limitations. We also included information on how users can compare their new estimates with previously available BoD estimates.

Conclusions

We introduced a reporting instrument for DALY calculations that can be used to document input data and methodological design choices in BoD studies. The application of such guidelines will enhance usability of BoD estimates for decision-makers as well as global, regional, and national health experts.

Key messages

A systematic literature review of burden of disease studies in Europe: next steps and implications for researchers

Facing the considerable variation in the computation of disability-adjusted life years (DALY), the European Burden of Disease Network (burden-eu) launched a series of systematic literature reviews (SLR) to explore the key variations in the assumptions used in the European burden of disease (BoD) assessments. The studies were evaluated in terms of pre-defined criteria, focusing on data sources used and on specific methodological and normative choices to assess BoD. Preliminary results show a wide variety in methodological assumptions used to quantify DALYs, but also important inconsistencies in the reporting of methods and particular assumptions. For instance, the quantification of uncertainties is not a common practice, even though most authors seem to be aware of the uncertainty in their DALY estimates and discuss uncertainties as an important study limitation. When uncertainties were quantified, different approaches were used, and described using inconsistent nomenclature. The results of the SLR show that there is a clear need for standardized reporting guidelines for DALY estimates. Such a tool could be based on quality assessment checklists already in place for clinical trials and observational studies (PRISMA, STROBE, CRD), and would require inclusion of the DALY's key methodological and normative choices. Standardized DALY reporting guidelines could serve multiple purposes. First and foremost, they would allow to increase the quality of reporting, thereby increasing the transparency and comparability of BoD studies. As a reference document, such guidelines would also help to harmonize nomenclature, which would further increase transparency and comparability. Last but not least, it would also serve as a capacity building tool, supporting researchers in understanding which methods and assumptions underlie the DALY metric. To address this need, the burden-eu network aims to play a driving role in the development of standardized DALY reporting guidelines.

A systematic literature review of studies estimating the risk factor attributable burden in Europe

Along with the computation of disability-adjusted life years (DALY), the Global Burden of Disease (GBD) study uses the comparative risk assessment method to estimate the burden attributable to risk factors (RF). The methodology used for GBD studies has undergone continuous improvements through the years and across many independent studies. The European burden of disease network launched a series of systematic literature reviews (SLR) to explore key assumptions used in the European burden of disease (BoD) assessments. The SLR will give an overview of existing studies, including those estimating the BoD attributable to RF and focus on the different computational approaches. The SLR will also help to identify ways to harmonize computational procedures to enhance the comparability of RF attributable burden. The SLR involved four parallel reviews: non-communicable diseases, communicable diseases, injuries and RF. For the latter, we used a search strategy with terms describing the population (GBD area “European region”) and terms specifically used in comparative risk assessments (comparative risk assessment [CRA], attributable mortality/burden/risk). Studies published between January 1990 and April 2020 were included, without language restrictions. The search strategy was run in PubMed, Web of Science, Cochrane, and Embase. OpenGrey, OAIster, CABDirect, WHO, and targeted public health agency websites were screened for indexed grey literature. In addition, burden-eu members were asked to supplement the list of publications with any material available in their national public health institutes. The title, abstract, and full-text screening resulted in the final inclusion of 114 publications. The list of publications includes peer-reviewed articles and reports showing a variability in CRA analysis (e.g. use of exposure-response function, relative risks) and other methodological choices. Further data extraction and analysis is in process and will be presented during the workshop.

The state of health in the European Union in 2019

Background

The European Union (EU) faces many health-related challenges. Accurate and timely data on mortality and morbidity from diseases and injuries and their trends over time are essential for health planning and priority setting.

Methods

We use the GBD 2019 study estimates and 95% uncertainty intervals for the whole EU and each country to evaluate age-standardized death, YLL, YLD and DALY rates for Level 2 causes. We evaluate trends by comparing estimates for the year 2019 with those for the year 2010.

Results

In 2019, the age-standardized death and DALY rates in the EU were 465.8 and 20 251.0 per 100 000 inhabitants, respectively. Between 2010 and 2019, there were significant decreases for age-standardized, death and YLL rates across EU countries. However, YLD rates remained mainly unchanged, with increases in the Netherlands and the ‘. The largest decreases in age-standardized DALY rates were observed for HIV/AIDS and sexually transmitted diseases and transport injuries (both -19%). On the other hand, only diabetes and kidney diseases showed a significant increase for age-standardized DALY rates in the EU (3.5%). Mental disorders showed an increasing age-standardized YLD rate, as well.

Conclusions

Overall, there was a visible trend of improvement in the health status in the EU with substantial differences between countries. EU health policy makers need to tackle incidence of diseases and injuries, with specific attention to causes such as mental disorders. There are many opportunities for mutual learning among otherwise similar countries with different patterns of disease.

Burden of diseases and injuries attributable to risk factors in the European Union in 2019

Background

In addition to information on mortality and morbidity from diseases and injuries, it is important to identify the attributable burden of risk factors to allow for health planning and prioritization.

Methods

For the whole EU and each country, using estimates and 95% uncertainty intervals from the GBD 2019 study, we report attributable (all-cause and by level 2 risk factors) age-standardized death and DALY rates, as well as summary exposure values (SEV). We evaluate trends by comparing estimates for the year 2019 with those for the year 2010.

Results

Age-standardized death and DALY rates attributable to risk factors declined by 10.7% (95%UI 13.8%-7.6%) and 9.1% (95%UI 12.0%-6.3%), between 2010 and 2019 in the EU. While there was a decreasing trend for both age-standardized death and DALY rates for almost all risk factors, some showed an increasing trend on SEV, including low physical activity and intimate partner violence.

Conclusions

Despite the improvement of health metrics attributable to risk factors, several modifiable behavioral and metabolic risk factors remain unchanged over the years. It is crucial to ensure a swift implementation of evidence-based policies and interventions in EU member states to achieve the targets of the Sustainable Development Goals.

An overview of burden of disease studies in Europe

Facing the considerable variation in the computation of disability-adjusted life years (DALY) in the numerous updates of the Global Burden of Disease (GBD) study and many independent studies, the European burden of disease network (burden-eu) launched a series of systematic literature reviews (SLR) to explore the key assumptions used in the European burden of disease (BoD) studies. The SLR will provide an overview of the existing BoD studies and the computational variations used and will also help identifying ways to harmonize the approaches enhancing the comparability of BoD estimates. The SLR was split in four parallel reviews: non-communicable diseases (NCDs), communicable diseases (CDs), injuries and risk factors. For the first three, the search strategy included terms describing the population (GBD area “European region”) and the BoD measures (years lived with disability, years of life lost, and DALYs). We included studies published between January 1990 and April 2020, without language restrictions. The search strategy was run in PubMed, Web of Science, Cochrane, and Embase. OpenGrey, OAIster, CABDirect, WHO and targeted public health agency websites were screened for grey literature. In addition, burden-eu members were asked to supplement the list of publications with any material available within their national public health institutes. Data extraction focused on methodological information. The title, abstract and full-text screening resulted in the final inclusion of 165 papers regarding NCDs, 189 with CDs, and 124 papers regarding injuries. The final list includes peer-reviewed articles and reports showing a variability in data sources used (e.g. patient medical records, disease registries, insurance claims sources) and model assumptions (e.g. use of multi-morbidity adjustments, use of disability weights). Further data extraction and analysis is in process, and will be presented during the workshop.

Fostering methodological advances and technical capacity building

Countries all over the world, and especially in Europe, are increasingly using the burden of disease approach to assess the health status of populations and to identify the main drivers of ill health. Thus, there is an increasing need for equitable capacity building on the one hand (including an improved understanding of the complex methods behind global and national burden estimates), and harmonization of methods on the other hand to keep the results comparable. Furthermore, involved researchers also strive for a platform to exchange experiences and foster collaboration.

To address the current challenges in burden of disease research, our COST Action CA18218-European Burden of Disease Network will build strongly on the COST mechanisms, such as short-term scientific missions and training schools to foster and increase capacity building activities across Europe. Our Action will also serve as a technical platform where knowledge and expertise can be shared among experienced and less experienced researchers. Collaboratively, the technical platform will provide unique opportunities for developing a joint research agenda in the domain of burden of disease, for fostering methodological developments, and for developing new collaborative research.

With this presentation, we aim to show how the COST Action is fostering methodological advances and technical capacity building, focusing on 1) the role and aim of short-term scientific missions including real case examples; 2) the concept and structure of the Action's training schools; and 3) examples of specific methodological activities underway as part of the Action. The session will conclude with an interaction with the audience during which the needs and expectations of the attendees will be elicited.

Burden of disease due to nitrogen dioxide exposure in Germany

Background

Numerous studies identified adverse effects of air pollution on health. According to the recent Global Burden of Disease Study about 2.9 million people died prematurely due to the effects of ambient particulate matter (PM) pollution in 2016, which resulted in about 70 million years of life lost (YLL). In addition to PM, a growing body of evidence shows convincing associations between nitrogen dioxide (NO2) with several health outcomes. The case study provides a health risk assessment for NO2 in Germany.

Methods

A systematic review was performed to select health outcomes with strong evidence for an association with NO2 and to derive an updated exposure-response function (ERF). The exposure assessment was performed on a 1x1 km2 grid by combining measured and modelled data (annual means of NO2 background concentration) with population density. Exposure data and the ERF were combined by the population attributable fraction formula. The main analysis was performed using a counterfactual of 10 µg/m3.

Results

Only for cardiovascular mortality the evidence for the association with long-term NO2-exposure was rated as “strong”. Thus, the main analysis merely included this outcome. For the year 2014, 5,966 (95% CI: 2,031-9,893) attributable deaths and 49,726 (95% CI: 16,929-82,456) YLL were estimated. Looking at time trends a decrease of disease burden was observed compared to the year 2007 where 7,832 (95% CI: 2,669-12,973) attributable deaths and 69.244 (95% CI: 23.601-114.690) YLL due to NO2 were calculated.

Conclusions

Our results show a considerable burden due to NO2 in Germany. Compared to previous estimates for PM (ca. 41,100 attributable deaths in 2014) the burden due to NO2 is much lower. However, due to methodological constraints we could not incorporate higher concentrations from traffic hotspots. This, and the fact that we only considered one health outcome in our main analysis, suggests that our results might be an underestimation.

Introduction to the Environmental Burden of Disease concept – history, methods and selected results

Background

The Environmental Burden of Disease (EBD)-concept was introduced by the World Health Organization to quantify the impacts of environmental risk factors on population health in a comprehensive and comparable way. Since the first Global Burden of Disease (GBD)-study the EBD-methodology was used in numerous global, regional and national assessments.

Methods

In the EBD-concept data from different sources are joined using a standardized framework. To calculate the EBD several steps need to be taken into account. First, the exposure of the selected population towards an environmental risk factor is estimated. In a second step, exposure data and information from an exposure-response-function are combined by using the population attributable fraction formula. In a last step, the attributable fraction (percentage) is multiplied by the disease burden resulting from a selected health outcome to estimate the share of disease burden attributable to the environmental risk factor.

Results

Since the first GBD-study several stakeholders have used the EBD-concept to estimate the disease burden attributable to environmental risk factors. This lead to an increased number of available data sets, which - due to the varying assumptions used in the models - are not ad hoc comparable among each other. Generally, the results of EBD-assessments are presented using disability-adjusted life years (DALY) as the core measure of burden of disease assessments. However, e. g. due to lack of data, assessments also focus on the number of attributable deaths, illnesses or single components of the DALY such as the years of life lost due to premature mortality (YLL).

Conclusions

The EBD-concept allows to compare the impact of environmental risk factors on population health. Though the general concept is widely standardized, assumptions on model parameters can lead to varying results. Therefore, when communicating EBD-results it is necessary to be very transparent about data and model inputs.