Global Health Topics: An Introduction (101)

In brief: Health topics are the subject headings that health agencies, researchers and websites use to organise knowledge about diseases, risk factors, population groups and health systems. The most widely used global framework, the Global Burden of Disease study, groups health problems into three families: communicable, maternal, neonatal and nutritional conditions; non-communicable diseases; and injuries. Cross-cutting themes such as health systems, equity and the environment sit on top of these.

Global health topics: a general introduction

Global health has been defined as an area for study, research and practice that places a priority on improving health and achieving health equity for all people worldwide (Koplan et al., 2009). The authors stress that “global” refers to the scope of a problem, not its location: tobacco control, obesity, injury prevention or the migration of health workers are global health topics even when they are studied in a single country.

How the world’s health problems are classified

The Global Burden of Disease (GBD) study organises diseases and injuries in a four-level hierarchy. Level 1 has the three broad families below; level 2 has 21 cause groups such as cardiovascular diseases or neoplasms; levels 3 and 4 list specific conditions (GBD 2017 Causes of Death Collaborators, 2018).

What is driving the agenda now

WHO’s latest Global Health Estimates, covering 2000 to 2023, count about 61 million deaths worldwide in 2023. Non-communicable diseases accounted for 74% of deaths, up from 58% in 2000, and eight of the ten leading causes of death were non-communicable, led by ischaemic heart disease, stroke and chronic obstructive pulmonary disease. Global life expectancy at birth recovered to 73.3 years after falling to 71.4 years in 2021 during the COVID-19 pandemic (Health Policy Watch, 2026). Alongside disease burden, the policy agenda is framed by Sustainable Development Goal 3, “ensure healthy lives and promote well-being for all at all ages”, whose targets include universal health coverage, maternal and child survival, communicable and non-communicable disease control, and road safety (United Nations, n.d.).

A categorised map of health topics

From a health topic to a research question

1. Check the burden. Use WHO or GBD estimates to see how many people are affected and whether the problem is growing.
2. Check the evidence gap. A quick scoping or umbrella review shows whether the question has already been answered; see Exploring Umbrella Reviews in Digital Health.
3. Narrow the scope. Move from a topic (“diabetes”) to a population, setting and outcome (“missed follow-up visits among older adults with type 2 diabetes in primary care”).
4. Link to policy. Questions tied to a national priority or an SDG target are easier to fund and more likely to be used.
5. Check feasibility. Data access, ethics approval, time and skills decide what is realistic.

The numbers behind the agenda: GBD 2023

The latest round of the Global Burden of Disease study, GBD 2023, was published in The Lancet in October 2025. It covers 375 diseases and injuries and 88 risk factors in 204 countries and territories and 660 subnational locations, from 1990 to 2023. Three findings matter for anyone choosing a health topic to work on:

• Risk factors explain about half of all health loss. Nearly 50% of the roughly 2.80 billion disability-adjusted life years (DALYs) lost in 2023 were attributable to the 88 risk factors analysed. The five largest contributors were high systolic blood pressure, particulate matter air pollution, high fasting plasma glucose, smoking, and low birthweight and short gestation (GBD 2023 Disease and Injury and Risk Factor Collaborators, 2025).
• The pandemic shock has left the rankings. COVID-19 was the leading age-standardised cause of death in 2021 but had fallen to 20th place by 2023, and ischaemic heart disease and stroke were again the two leading causes (GBD 2023 Causes of Death Collaborators, 2025).
• People die older, but very unequally. The global mean age at death rose from 46.8 years in 1990 to 63.4 years in 2023. In 2023 it reached 80.9 years for women in high-income countries but only 35.6 years for men in sub-Saharan Africa (GBD 2023 Causes of Death Collaborators, 2025).

Money and governance: the shocks of 2025 and 2026

Two changes in global health governance are reshaping research and policy priorities. The first is money. IHME estimated that development assistance for health (DAH) fell to about US$39 billion in 2025, its lowest level in 15 years and less than half the 2021 peak of US$80 billion; the largest cuts came from the United States, the United Kingdom, France and Germany (Institute for Health Metrics and Evaluation [IHME], 2025). IHME has since revised its series, and its October 2026 update estimated a further fall of about 5% in 2026, with sub-Saharan Africa absorbing the largest reduction (Apeagyei et al., 2026).

The second is governance. The United States formally left the World Health Organization on 22 January 2026, one year after giving notice (U.S. Department of Health and Human Services, 2026). In the opposite direction, the World Health Assembly adopted the WHO Pandemic Agreement by consensus on 20 May 2025, only the second treaty negotiated under Article 19 of the WHO Constitution after the Framework Convention on Tobacco Control (World Health Organization [WHO], 2025). The Agreement cannot open for signature until an annex on Pathogen Access and Benefit-Sharing (PABS) is adopted. Member States missed the May 2026 deadline and extended the negotiations, with the outcome due at the 80th World Health Assembly in May 2027 or at an earlier special session (WHO, 2026).

Universal health coverage: progress, then a slowdown

The 2025 UHC Global Monitoring Report shows that the service coverage index rose from 54 to 71 points between 2000 and 2023, and that the share of people facing financial hardship from out-of-pocket spending fell from 34% to 26%. Even so, about 4.6 billion people lacked access to essential health services and 2.1 billion faced financial hardship, and on current trends the index will reach only 74 by 2030 (WHO & World Bank, 2025). Most of the gain came from infectious disease programmes. That is why services for non-communicable diseases, primary care and financial protection are now the central research gaps.

Where to find reliable data on a health topic

Our comparison of the top health information websites shows how the leading sites organise and present health topics for the public.

Sources for this introduction

• Apeagyei, A., Elliott, H., DeJarnatt, D., Shyong, C., Leach-Kemon, K., & Dieleman, J. L. (2026, October 20). The state of global health funding: October 2026. Think Global Health. https://www.thinkglobalhealth.org/article/the-state-of-global-health-funding-october-2026
• GBD 2017 Causes of Death Collaborators. (2018). Global, regional, and national age-sex-specific mortality for 282 causes of death in 195 countries and territories, 1980–2017: A systematic analysis for the Global Burden of Disease Study 2017. The Lancet, 392(10159), 1736–1788. https://doi.org/10.1016/S0140-6736(18)32203-7
• GBD 2023 Causes of Death Collaborators. (2025). Global burden of 292 causes of death in 204 countries and territories and 660 subnational locations, 1990–2023: A systematic analysis for the Global Burden of Disease Study 2023. The Lancet, 406(10513), 1811–1872. https://doi.org/10.1016/S0140-6736(25)01917-8
• GBD 2023 Disease and Injury and Risk Factor Collaborators. (2025). Burden of 375 diseases and injuries, risk-attributable burden of 88 risk factors, and healthy life expectancy in 204 countries and territories, including 660 subnational locations, 1990–2023: A systematic analysis for the Global Burden of Disease Study 2023. The Lancet, 406(10513), 1873–1922. https://doi.org/10.1016/S0140-6736(25)01637-X
• Health Policy Watch. (2026, October 2). COVID-19 drops out of world’s top 10 causes of death for first time since pandemic began. https://healthpolicy-watch.news/covid-19-drops-out-of-worlds-top-10-causes-of-death-for-first-time-since-pandemic-began/
• Institute for Health Metrics and Evaluation. (2025). Financing Global Health 2025: Cuts in aid and future outlook. IHME.
• Koplan, J. P., Bond, T. C., Merson, M. H., Reddy, K. S., Rodriguez, M. H., Sewankambo, N. K., & Wasserheit, J. N. (2009). Towards a common definition of global health. The Lancet, 373(9679), 1993–1995. https://doi.org/10.1016/S0140-6736(09)60332-9
• U.S. Department of Health and Human Services. (2026, January 22). Fact sheet: U.S. withdrawal from the World Health Organization. https://www.hhs.gov/press-room/fact-sheet-us-withdrawal-from-the-world-health-organization.html
• United Nations. (n.d.). Goal 3: Ensure healthy lives and promote well-being for all at all ages. https://sdgs.un.org/goals/goal3
• World Health Organization & World Bank. (2025). Tracking universal health coverage: 2025 global monitoring report. https://www.worldbank.org/en/topic/universalhealthcoverage/publication/2025-global-monitoring-report-gmr
• World Health Organization. (2025, May 20). World Health Assembly adopts historic Pandemic Agreement to make the world more equitable and safer from future pandemics. https://www.who.int/news/item/20-05-2025-world-health-assembly-adopts-historic-pandemic-agreement-to-make-the-world-more-equitable-and-safer-from-future-pandemics
• World Health Organization. (2026, May 19). Seventy-ninth World Health Assembly: Daily update, 19 May 2026. https://www.who.int/news/item/19-05-2026-seventy-ninth-world-health-assembly—daily-update–19-may-2026