Modern Burden of Disease Studies as a Basis for Decision-Making Processes in Public Health

Editorial to accompany the articles: “Years of Life Lost to Death—A Comprehensive Analysis of Mortality in Germany Conducted as Part of the BURDEN 2020 Project” by Annelene Wengler et al. and “The COVID-19 Disease Burden in Germany in 2020—Years of Life Lost to Death and Disease Over the Course of the Pandemic” by Alexander Rommel et al. in this issue of Deutsches Ärzteblatt International

Predominantly owing to the SARS-CoV-2 pandemic, the challenges involved in establishing the burden of disease caused by a given illness have become clear, both to the general public and to medical professionals, over the past year. Before the pandemic the determination of the burden of a disease was often seen as a descriptive task primarily serving the purpose of surveillance, but with its onset questions about the burden of disease that could be anticipated in specific situations suddenly formed the focus of public and political discussion. Particularly when evaluating complex interventions with long-term effects (e.g., non-pharmaceutical interventions [NPI] to hinder the transmission of SARS-CoV-2), it is necessary to to be able to estimate the burden of disease at population level in order to facilitate decision-making processes (e.g., pandemic with NPI versus pandemic without NPI). The experience of this pandemic has shown clearly that rapid evaluation even of simple burden of disease indicators such as incidence, mortality, and case fatality ratio is almost impossible in the case of a novel disease (1).

Disability-adjusted life years as an overall indicator of disease burden

Moreover, focusing on such simple binary indicators (infected versus uninfected, deceased versus not deceased) is inadequate for the measurement of the burden of disease. For instance, deaths are all weighted identically whatever the age of the deceased, and chronic health impairments caused by the disease are ignored completely.

Chris Murray and Alan Lopez, two of the founders of the Global Burden of Disease Study—initiated in the early 1990s by the World Health Organization (WHO) and the World Bank together with the Harvard School of Public Health—therefore developed the concept of disability-adjusted life years (DALY) as a global indicator. This measure combines the shortening of life due to death from the disease (years of life lost, YLL) and the healthy years of life lost owing to disease-associated impairments (years lived with disability, YLD) (2, 3).

The article by Wengler and colleagues (4) in this issue is dedicated to the estimation of the YLL due to various causes of death in Germany. By ranking the most frequently occurring causes of death first by YLL and second by absolute numbers of deaths, the authors clearly show the difference in the perception of the burden of disease associated with a specific illness that emerges when one talks in terms of YLL rather than the absolute number of fatalities. At the same time, the article points up the problems involved in conducting burden of disease studies with the goal of assigning disease burden to defined causes: For example, it is not always possible to allocate deaths and YLL to ICD codes with certainty, because the codes in the records overlap or are non-informative.

Health consequences of the pandemic

In another article in this issue, Rommel and colleagues go a step further and set themselves the goal of presenting the burden of disease caused by COVID-19 in Germany in the year 2020, in terms of both YLL and YLD (5). This is important because it represents the first estimation for Germany of a crucial endpoint for decision-making processes during the pandemic. At the same time, a few inherent weaknesses of this indicator become particularly evident during the pandemic. For instance, at the current time the dimensions of the YLD are entirely unclear. The long-term consequences of infection with SARS-CoV-2 (“long COVID”) have not yet been investigated in sufficient depth to make any contribution to the evidence base. It was for this reason that Rommel et al. chose to leave this aspect out of their calculations, but by doing so they underestimate to an unknown extent the DALYs connected with COVID-19. Furthermore, the health consequences of the pandemic are not restricted to the DALYs caused directly by COVID-19, but also include indirect effects, both of the pandemic itself and of countermeasures. To date, there are hardly any primary data that could be used in burden of disease analyses. It is important to emphasize that the authors’ estimates of the disease burden associated with COVID-19 in 2020 were made in the context of massive population-wide interventions, so that the anticipated burden of disease would be far higher without such interventions.

Burden of disease studies as central evidence base for necessary adjustments

In contrast to emerging infectious diseases, modern burden of disease studies for non-communicable diseases often have ready access to adequate primary data. Such studies have long been established, for example, for cancer and cardiovascular disease (6, 7) and play a considerable role in the allocation of resources for health research.

It is a cause for celebration that the systematic burden of disease studies that began in Germany in the framework of European consortia (8) are being continued in the context of the BURDEN 2020 project and also extended to smaller spatial units at regional level (9)—a path also trodden by the Global Burden of Disease Study (10). In recent years burden of disease studies, particularly in the area of social epidemiology, have become established as a central evidence base for necessary adjustments of healthcare provision.

The two burden of disease analyses published in this issue of Deutsches Ärzteblatt International (4, 5) have their origin in the Epidemiology and Health Monitoring Department of the Robert Koch Institute, headed until his premature death in December 2020 by PD Dr. Thomas Lampert. Like no-one else in Germany, Thomas Lampert stood for the scientific analysis of social determinants of health in society. His life and work are honored (in German) in an obituary in the Personalia section of the current issue of Deutsches Ärzteblatt.

Conflict of interest statement
The author declares that no conflict of interest exists.

Translated from the original German by David Roseveare

Corresponding author
Prof. Dr. med. André Karch, MSc
Institut für Epidemiologie und Sozialmedizin der Universität Münster
Albert-Schweitzer-Campus 1, Gebäude D3
Domagkstr. 3, 48149 Münster, Germany

Cite this as:
Karch A:
Modern burden of disease studies as a basis
for decision-making processes in public health.
Dtsch Arztebl Int 2021; 118: 135–6.
DOI: 10.3238/arztebl.m2021.0152

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