Global Health Data Explorer: Our World in Data

Why do different sources disagree on numbers for the same metric?

Collecting accurate data on global health is difficult: we will never know exactly which diseases or injuries are affecting people around the world at any given time. In the absence of perfect data, health researchers have several ways to try to estimate the burden of global health outcomes. These estimates are what we present in the Global Health Explorer.

We obtain the Global Health Explorer data from three main sources, as follows:

Institute for Health Metrics and Evaluation Global Burden of Disease Study World Health Organization Global Health Estimates World Health Organization Global Health Observatory

Each of these sources has slightly different methods for estimating the burden of disease and causes of death, and in some cases the definition of the diseases and injuries in question differs slightly.

Methodological differences

Global Burden of Disease (IHME)

In the Global Burden of Disease study, the IHME uses a wide range of input data, including but not limited to census data, household surveys, civil registration and vital statistics, disease registries, use of health services, air pollution monitors, etc. satellite imagery, disease reports and other sources. These data are available through scientific journals, reports, online databases, books, news reports and other resources. For most diseases and injuries, the data are used as input to a series of standardized models that are used to generate estimates of each disease or injury for all age groups, sexes, locations and years.

Since the publication of its Global Burden of Disease study in 2017, the IHME has used its own population estimates. These differ from those used by the UN Population Division, which are used by the World Health Organization (WHO). This key difference propagates across all resulting health datasets. Even if the IHME and WHO assume the same health burden and mortality rates, this difference in population estimates means that many of their population-adjusted figures would be different.

Full details on how the IHME global burden of disease is calculated are available here and here.

Global Health Estimates (WHO GHE)

Global health estimates are primarily calculated using cause-of-death statistics reported to WHO by individual countries.

These vital registration (VR) statistics are submitted to the WHO mortality database annually by country, year, cause, age and sex. These data are included in the overall health estimates if they meet criteria that assess completeness and quality. Because many countries do not meet these criteria, the GHE does not include VR statistics for all countries.

There are a number of specialized WHO groups and UN agencies that collect topic- or disease-specific data. The HIV and AIDS dataset, compiled and published by UN AIDS, is one example. Estimates based on VR data are compared with data from WHO specialized groups and UN agencies and adjustments are made if necessary.

When virtual reality data cannot be used and other nationally representative cause-of-death data are not available, the World Health Organization adopts IHME Global Burden of Disease data to fill these empty. Full details on how the WHO global health estimates are calculated are available here.

World Health Observatory (WHO GHO)

The WHO Global Health Observatory brings together a large number of variables produced by WHO and specialized UN agencies.

The variables found in the Global Health Observatory are limited to the leading causes of death and injury. This means that the WHO GHO is less ‘complete’ than the IHME Global Burden of Disease Study and the WHO GHE in terms of the diseases included.

The method used to produce each of these variables is different and tailored to the specific cause of death or injury. This is a different approach to both the global burden of disease (IHME) and global health estimates (WHO) which attempt to use a consistent modeling approach for all causes of death and injury. Furthermore, Global Health Observatory variables are not consistently disaggregated by age or sex. Instead, they show what data is available and most relevant to the given variable.

The full list of variables available in the Global Health Observatory is available here, each with its own associated metadata and methods.

Differences in the definition of the disease

Diseases and injuries presented in the Global Health Explorer are often aggregates of multiple similar causes of death. For example, “Fall Deaths” includes 20 different types of falls that are combined into this variable.

Individual causes of death are associated with an International Classification of Diseases (ICD) code. The tenth version of the ICD codes is used in the most recent global health and global burden of disease estimates and is called ICD-10. For example, “Falling tree” has the ICD-10 code “W14”, and the ICD-10 codes for all “Death from falls” are “W00-W19”.

Both IHME and WHO follow the same definition of “Death from falls”, but for some other causes of death, their definitions of the same aggregate cause of death do not include exactly the same ICD-10 codes. For example, the ICD-10 code “F02.3 – A dementia that develops in the course of established Parkinson’s disease” is included as “Dementia” in the WHO Global Health Estimates, but as “Parkinson’s disease” in the IHME Global Burden of Disease.

These slight differences in disease definition may also contribute to the different values ​​we see when looking at the same metric from different sources. ICD-10 codes used by IHME to define causes of death can be found here and ICD-10 codes used by WHO can be found here.

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