menu

Institute of Dentistry

Research menu

Global Burden of Disease Study: Oral Health

Associated Research:  Patient and Population Orientated Research

Professor Marcenes led the Oral Health Research within the new Global Burden of Disease study (the GBD Study). The new Global Burden of Diseases, Injuries, and Risk Factors Study commenced in the spring of 2007 and was the first major effort since the original GBD 1990 Study to carry out a complete systematic assessment of global data on all diseases and injuries. GBD 2010 has produced comprehensive and comparable estimates of the burden of diseases, injuries and risk factors for two time periods, 1990 and 2005, with projections for 2010. This project was funded by the Bill and Melinda Gates Foundation.

The GBD Study brought together a community of experts and leaders in epidemiology and other areas of public health research from around the world to measure current levels and recent trends in all major diseases, injuries, and risk factors, and to produce new and comprehensive sets of estimates and easy-to-use tools for research and teaching. This ambitious effort was conducted systematically and transparently; both its methods and results were made available to the public.

The new GBD Study was led by a consortium including the Harvard Initiative for Global health at Harvard University, the Institute for Health Metrics and Evaluation at the University of Washington, Johns Hopkins University, the University of Queensland, and the World Health Organization (WHO).

The GBD Study focussed on more than 175 diseases and injuries and more than 43 risk factors for 21 regions of the world. It served to systematically incorporate the evidence on each major disease and risk factor into a coherent set of epidemiological estimates. It has also provided an opportunity for concerted work on new age- and sex-specific mortality estimates, disability weight measurement, estimates of probabilities of disabling sequelae, standardization of tools and methods for resolving inconsistencies, dealing with missing data and quantifying uncertainty. The GBD Study conducted epidemiological reviews of all diseases, injuries, and risk factors; estimated mortality and causes of death for all countries in the world; derived new disability weights for an updated list of disabling sequelae, all leading to final, consistent and comprehensive estimates of the burden of diseases, injuries and risk factors for 1990 and 2005.

Background

The original Global Burden of Disease Study (original GBD 1990 Study) was commissioned by the World Bank in 1991 to provide a comprehensive assessment of the burden of 107 diseases and injuries and ten selected risk factors for the world and eight major regions in 1990 (1). The methods of the original GBD 1990 Study created a common metric to estimate the health loss associated with morbidity and mortality. It generated widely published findings and comparable information on disease and injury incidence and prevalence for all world regions. It also stimulated numerous national studies of burden of disease. These results were used by governments and non-governmental agencies to inform priorities for research, development, policies and funding.

The principle guiding the burden of disease approach is that the best estimates of incidence, prevalence, and mortality can be generated by carefully analysing all available sources of information in a country or region, and correcting for bias. The disability-adjusted life year (DALY), a time-based measure that combined years of life lost due to premature mortality and years of life lost due to time lived in health states less than ideal health was developed to assess the burden of disease. The GBD represented a major step in quantifying global and regional effects of diseases, injuries, and risk factors on population health.

In 2000, the World Health Organization began publishing regular GBD updates for the world and 14 regions (2). These revisions were aided by methodological improvements and more extensive data collection that covered key aspects of the GBD, including mortality estimation, cause of death analysis, and measurement and valuation of functional health status. Standardized concepts and approaches to comparative risk assessment were applied to over 25 risk factors. New estimates for 2001 were published as part of the second revision of the Disease Control Priorities Project (3). In addition to these continuing efforts for better epidemiological quantification, the philosophical underpinnings for quantifying population health have been extensively explored as part of the overall effort to foster summary measures of population health.

Research

Objectives

Despite the considerable efforts made and the methodological improvements achieved, important opportunities remained to greatly advance the quantification of the burden of diseases, injuries and risk factors.

First, there had not been a complete systematic assessment of the data on all diseases and injuries since the original GBD 1990 Study. Such an assessment was particularly relevant because new sources of primary data had become available including vital statistics data, Demographic and Health Surveys, Multiple Indicator Cluster Surveys, World Health Surveys and several national health interview and examination surveys. Second, new methods for estimating adult mortality, analysing verbal autopsy data, modelling cause of death composition, computing attributable fractions for multiple risk factors, correcting for differential item functioning in health surveys, and imposing internal consistency constraints could be brought to bear. Third, better population-based methods and data had become available to develop improved disability weights for the health states included in the GBD Study. Finally, there is a large community of epidemiologists and public health specialists who are familiar with the burden of disease concepts and methods in many countries and regions, who were able to contribute to methodological and empirical improvements.

The new GBD Study achieved two major objectives. First, it produced estimates of the burden of diseases, injuries and risk factors for 1990 and 2005, using new data and improved techniques. The GBD Study was collaborative at all levels, with coordination by a team of public health researchers from a number of leading research institutions and engagement of experts across study regions. The estimates, organized in 21 regions covering the globe, were comprehensive and consistent.

Second, the GBD Study has developed a series of tools for use by specific audiences, to standardize and broaden the burden of disease research and analysis. Revised computational tools allow researchers around the world to apply the GBD burden of disease and comparative risk assessment techniques in a systematic way. Tailored publications help policymakers and non-research audiences to interpret GBD concepts and utilize study results.

Organisation

A Core Team of scientists and methodologists coordinated the GBD Study and ensured its steady progress along a 45-month time frame. The Core Team reunited the authors of the original GBD 1990 Study and engaged new leaders in the global health field to design and coordinate the research.

An invitation for participation in the GBD Study was announced in the summer of 2007, and more than 750 experts’ applications were received. The experts were organized into approximately 45 scientific Expert Groups for specific diseases, injuries, and risk factors.

These groups conducted systematic reviews of the incidence and prevalence of diseases and disabling sequelae, and of exposure to and effects of risk factors. They communicated their figures at defined intervals to the other Expert Groups and the Core Team in order to ensure consistency across conditions.

Responding to critiques and improvements in the field, the new GBD Study has made major progress in disability assessment, using new survey instruments to update disability weights and collect data on health states. Consistency checks and peer reviews occured throughout the GBD Study to ensure that estimates of mortality, burden of disease, injuries and risk factors are systematically and cautiously generated. As an important quality check, the GBD Study embedded feedback and discourse among participants into its design.

Roles and Responsibilities

The GBD Study has a hierarchy designed to facilitate coordination and enhance collaboration. Several specific groups have complementary responsibilities. The External Advisory Board served as a primary liaison to key stakeholders in research and policy networks for global health. The Core Team’s principal role was to co-ordinate the project overall. Expert Groups were organised to be loosely coincident with condition specific or risk factor-specific interests. These Expert Groups were ordered into five Clusters, each with a Cluster Leader for management purposes. Each group featured a number of specific roles as described below, which further facilitated good communications.

External Advisory Board

The External Advisory Board served as a primary liaison to key stakeholders in research and policy networks for global health. It advised the Core Team on a variety of strategic matters. The Board’s principal goal was to broaden the global impact of the burden of disease work. Toward that end, it assisted in securing outlets for publication and presentation of findings, and advised on ways of sharing these with the public, NGOs, policymakers, and the research community as part of a broader dissemination strategy.

Finally, the External Advisory Board also functioned as a sounding board for the Core Team, raising questions and giving feedback on the issues of study design, inclusion of participants, and fundraising.

GBD core team

The Core Team consists of a group of scientists from Harvard University, the Institute for Health Metrics and Evaluation at the University of Washington, Johns Hopkins University, the University of Queensland, and the World Health Organization.

The primary role of the Core Team was to coordinate the overall project, technically as well as logistically. The institutional leader of the project was the Institute for Health Metrics and Evaluation at the University of Washington, where the project’s core management was based. The Core Team has:

  • Ensured consistency of the study approach across the different Expert Groups.
  • Supported the Expert Groups in their work by providing templates; answering questions about estimation techniques and approaches; providing guidance on epidemiological reviews; conducting burden estimation and comparative risk assessment training for interested participants; and ensuring that data resources are shared across the project.
  • Defined age groups and regions into which the final estimates were disaggregated.
  • Finalised a set of diseases, injuries, and risk factors for which estimates were produced based upon the collective input of the Expert Groups.
  • Collected and assessed centralized data sources for overall mortality by age and region.
  • Established mortality envelopes by assessing total child and adult mortality for all countries by age and sex.
  • Collected and assessed centralised data sources for causes of death (e.g. national vital registration data, disease registries, major health surveys) together with the epidemiological information collated by the Expert Groups that can be used for cause of death estimation.
  • Finalised a list of disabling sequelae based upon the collective input of the Expert Groups and formalised definitions for them that are consistent regardless of the underlying disease cause of the sequelae.
  • Established impairment envelopes for selected impairments including vision loss, hearing loss, mental retardation and consulted with relevant expert groups to ensure consistency of estimates for related disabling sequelae for specific causes.
  • Carried out data collection to inform the estimation of disability weights for disabling sequelae using standardised protocols.
  • Estimated the prevalence by age, sex and region of key impairments that are disabling sequelae of more than one disease including cognitive impairment, anaemia, visual impairment and hearing loss.
  • Performed a set of analytic consistency checks of submitted data and preliminary estimates across age, region, sex, and condition.
  • Organised peer review of the epidemiological evidence and preliminary estimates produced by the Expert Groups.
  • Created and maintained an archive of data sources used in the epidemiological reviews.
  • The archive included a bibliographic list of sources, and where possible – the actual datasets or source articles themselves.
  • Created tools for use in estimation and analysis. Prior to being distributed to a wider audience, the tools were shared with participants and improved as a result of their feedback.
  • Finalised coherent and consistent estimates of the burden of diseases, injuries, and risk factors. Published this set of estimates as the ultimate end-product of the GBD Study on behalf of the project participants. The final estimates include total mortality, years of life lost, and years lived with disability caused by diseases and injuries, disaggregated by sex, age, and region. In addition, the final estimates comprise mortality and burden of disease attributable to major risks disaggregated by sex, age, and region.

Cluster Leader

The Expert Groups were organized into five Clusters for management purposes. Note that the five Clusters were not intended to be substantively significant divisions of the overall GBD; they were selected for managerial effectiveness across the collaborating institutions. Each Cluster had a Cluster Leader who is a member of the Core Team. As expected, some Expert Groups worked with others outside of their own Cluster. The Cluster leaders facilitated this process. Cluster Leaders:

  • Provided a direct link back to the Core Team for any questions, concerns or requests from the Expert Groups.
  • Helped to direct questions about burden of disease estimation and comparative risk assessment techniques and approaches to the right members of the Core Team.
  • Worked with the Expert Groups to address the challenges encountered during the epidemiological reviews.
  • Facilitated communication and coordination among the groups, i.e. regularly contacting the Expert Groups’ Leaders to summarize progress to date, report findings, and ensure that different groups dealing with similar challenges were communicating effectively.
  • Provided initial feedback on the consistency of the produced results.
  • Provided analytical support when needed.

Expert Groups

The Expert Groups were organized to be loosely coincident with condition-specific or risk factor-specific interests. Each group had an Expert Group Leader or Co-Leaders, Core Members, and Corresponding Members. Each Expert Group agreed upon and submitted its own estimates and epidemiological reviews to the Core Team, and:

  • Drafted precise definitions of each disease, injury, and risk factor in consultation with the Cluster Leader and the Core Team.
  • Drafted precise definitions of sequelae mapped to conditions in consultation with the Core Team, especially to ensure that sequelae definitions were consistent across the project.
  • Where groups were working on diseases and injuries, undertook systematic reviews of both published and unpublished literature and studies to amass data on incidence and duration, or on other inputs like prevalence, remission, and case fatality that allow estimating incidence and duration.
  • Where groups were working on risk factors, undertook a systematic review of all published and available unpublished epidemiological studies, health surveys, and health examination surveys. This included both randomized and observation studies, as well as biological evidence to establish the disease and injury outcomes associated with each risk factor and other data sources that can be used to estimate risk factor exposure. This was also used to establish the magnitude of their hazardous effects for these diseases and injuries.
  • Created an explicit audit trail of all sources and data used. This work was aided by templates provided by the Core Team which were adapted to fit the needs of individual groups.
  • Conducted all reviews according to the guidelines provided in the previous manual to ensure that the Expert Groups were consistent in their approach.
  • Revised the epidemiological reviews and estimates taking into consideration the feedback from the Core Team and the peer review process. The basic parameters were that all epidemiological reviews must cover data from 1990 to 2005, and be age-, region-, and sex- specific whenever possible.

Expert Group Leader

Each Expert Group had a designated Leader or Co-Leaders whose primary responsibility was to facilitate the work of the group as a whole. Professor Wagner Marcenes is the expert group leader for Oral Health. The Expert Group Leader was responsible for achieving consensus on the estimates and data that are presented to the Core Team. He/she served as the focal point for any funding proposals submitted by the Expert Group to the Core Team. The Expert Group Leaders contacted the Cluster Leaders most frequently in order to draw attention to questions as they arose, facilitated communication among members, and ensured that the GBD Study deadlines were met.

Expert Group Core Member

Each Expert Group had several Core Members. They met on a regular basis, occasionally in person but more frequently by phone and e-mail, to review progress to date and formulate strategies for pursuing the work further. They carried out the epidemiological reviews most directly and undertook the key elements of the Expert Group’s responsibilities outlined above.

The following Oral Health Expert Group Core members drafted precise definitions of dental carries, periodontal disease and tooth loss.

D Brennan, J Frencken, S Griffin, R Lalli, MF De Lima Navarro, G Netuveli, PE Petersen, C Pine, M Thomson, E Treasure, J Spencer.

The following Oral Health Expert Group Core members extracted and contributed to the data analysis.

Data extractors: M Dahiya and B Bhandari.

Data analysis: E Bernabe.

Expert Group Corresponding Member

Each Expert Group had numerous Corresponding Members. These individuals did not participate in the regular meetings, but received the materials and latest data from the Expert Group on a periodic basis. They were given an opportunity to review these materials and data, and to provide input on the work. On occasion, they were asked to add to specific components or give advice on particular elements of the GBD Study.

Cross-cutting Issues Core Member

These individuals have either expertise that reaches across the clusters, experience and insights from their past and current work which were valuable to the project, or other characteristics and interests such that their participation in a broader-focused group was ideal. Cross-Cutting Issues Core Members were coordinated by a member of the Core Team and asked for their input, advice and feedback at critical junctures of the GBD Study.

Cross-cutting Issues Corresponding Member

These individuals were periodically called on to review the ongoing work of the Core Members of the Cross-Cutting Issues Expert Group. Occasionally they were asked to add  to specific components or offer their advice on a discrete element of the GBD Study. The Expert Group Leader or a member of the Core Team contacted them with progress reports or to share the ongoing research.

Benefits

The GBD Study provides four key benefits as a source of accurate knowledge and a vital tool for informed decision-making. First, the GBD Study separates epidemiological assessment from advocacy, creating evidence-based pictures of health patterns that can subsequently motivate responsible policy formulation and research. Major infectious diseases such as HIV, TB, and malaria have absorbed a great deal of attention, while “new” conditions, such as hearing loss and migraine, have only recently been included in the public health agenda. The new GBD Study uses standard measures to ensure that all conditions receive systematic and objective analyses.

Second, the GBD Study combines information on disease and risk factor causes of premature mortality, morbidity, and disability to present a balanced assessment of health problems. The first GBD project brought visibility and legitimacy to conditions like depression and paralysis, which cause great suffering with little associated mortality, as well as conditions like road traffic injuries, which were formerly outside the scope of mainstream public health. The new GBD Study has the potential to change common perceptions of global health.

Third, the GBD Study assesses the magnitude of health problems using standard units of measurement, such as disability-adjusted life years (DALYs). This study feature allows for lives in every part of the world to be valued equally, and creates a common unit of currency for making decisions about the costs and benefits of various health interventions.

Fourth, the GBD Study was focussed from the outset on education and transparency, incorporating features such as an interactive website where experts were able to post information and actively discuss the GBD Study. Broadening the global community’s engagement with population health metrics is a priority of the GBD Study.

Improving the health and well-being of the world’s population is a moral imperative and is essential for global stability and progress. The vast energies, technologies, and resources that are pouring into global health have given us the capacity to fight disease, remedy disability, and address the deep inequalities in health between populations. The new round of the Global Burden of Diseases, Injuries, and Risk Factors Study provides the tools and knowledge to inform efforts for making truly effective interventions possible.

Key Publications

View a recent lecture about the Global Burden of Oral Diseases [PDF 229KB] by Professor Marcenes at BASCD (British Association for the Study of Community Dentistry) Spring Conference, 2013, Buxton.

GBD presentation WCPD 2013 Budapest, IADR World Congress on Preventative Dentistry [PDF 844KB]

W. Marcenes, N.J. Kassebaum, E. Bernabé, A. Flaxman, M. Naghavi, A. Lopez, and C.J.L. Murray (2013) Global Burden of Oral Conditions in 1990-2010: A Systematic Analysis, J DENT RES, published online 29 May, 2013

W.V. Giannobile (2013) Our Duty to Promote Global Oral Health, J DENT RES, first published on May 29, 2013

Lim SS, Vos T, Flaxman AD ... Marcenes W ... Lopez AD, Murray CJ, Ezzati (2013) 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. M. Lancet. 15;380(9859):2224-60.

Murray CJ, Vos T, Lozano R ... Marcenes W ... Lopez AD. (2013) 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. 15;380(9859):2197-223.

Vos T, Flaxman AD, Naghavi M ... Marcenes W ... Lopez AD, Murray CJ. (2013) 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. 15; 380(9859):2163-96.

Salomon JA, Vos T, Hogan DR ... Marcenes W ...  Murray CJ (2013) Common values in assessing health outcomes from disease and injury: disability weights measurement study for the Global Burden of Disease Study 2010. Lancet. 15;380(9859):2129-43.

Contact

Professor Marcenes
Professor in Oral Epidemiology

w.marcenes@qmul.ac.uk
+44 (0)20 7882 8650

Centre for Clinical & Diagnostic Oral Sciences
5th Floor, Institute of Dentistry
Barts and the London School of Medicine & Dentistry
Turner Street
Whitechapel
London
E1 2AD
UK

Return to top