Report on Global Trends, Health Inequalities, and Projections in the Burden of Neglected Tropical Diseases and Malaria (1990–2021)

Abstract

Neglected Tropical Diseases (NTDs) and malaria remain critical global public health challenges, predominantly affecting low-income countries. Despite recent declines in disease burden, significant health inequalities persist, especially in tropical, poverty-stricken regions. Climate change is projected to exacerbate these burdens, disproportionately impacting vulnerable populations. This report analyzes global trends, spatial distribution, health inequalities, and future projections of NTDs and malaria burden using data from the Global Burden of Disease Study (GBD) 2021. Emphasis is placed on the Sustainable Development Goals (SDGs), particularly SDG 3 (Good Health and Well-being), SDG 1 (No Poverty), and SDG 10 (Reduced Inequalities).

Background

NTDs are a diverse group of diseases caused by various pathogens, affecting over 1.6 billion people worldwide, including more than 500 million children. Malaria, a deadly parasitic disease transmitted by mosquitoes, continues to pose significant control challenges due to drug resistance and parasite adaptability.

Both NTDs and malaria are environmentally linked, endemic in tropical and subtropical regions, and disproportionately affect impoverished populations. The World Health Organization (WHO) has developed roadmaps for controlling and eliminating these diseases, aligning with the SDGs to reduce health inequalities and promote global health equity.

Methods

Data Source

Data were sourced from the GBD 2021, covering 371 diseases and injuries across 204 countries from 1990 to 2021. Countries were categorized by Socio-Demographic Index (SDI) into five levels: Low, Low-middle, Middle, High-middle, and High SDI.

Data Inclusion and Exclusion Criteria

• Included: NTDs and malaria as classified by GBD 2021, incidence, mortality, and Disability-Adjusted Life Years (DALYs) data from 1990–2021, and environmental covariates.
• Excluded: Diseases not classified as NTDs or malaria, countries with incomplete data, and modifiable socioeconomic covariates except SDI.

Case Definitions

• NTDs and Malaria: Includes diseases such as dengue, lymphatic filariasis, schistosomiasis, malaria, and others.
• Natural Environment Index (NEI): Composite indicator quantifying environmental impact on disease burden.
• Socio-Demographic Index (SDI): Composite measure of social development based on fertility, education, and income.

Statistical Analyses

• Analysis of disease burden composition differences by SDI regions.
• Evaluation of regional, age, and gender differences and trends using Estimated Annual Percentage Change (EAPC).
• Inequality assessment using Slope Index of Inequality (SII) and Concentration Index (CI).
• Construction of NEI using environmental covariates and regression models.
• Frontier analysis to assess governance potential in disease burden management.
• Bayesian Age-Period-Cohort (BAPC) model to forecast disease burden trends (2022–2041).

Results

Regional and Temporal Differences in Disease Composition

• Malaria remains the leading cause of NTDs and malaria burden globally, especially in Low and Low-middle SDI regions.
• Other NTDs such as schistosomiasis and dengue have increased in ranking over time.
• High SDI regions show negligible malaria burden but increased contributions from other NTDs.

Distribution and Trends Across Regions

• From 1990 to 2021, age-standardized mortality and DALY rates declined globally, but incidence rates remained stable.
• Western Sub-Saharan Africa bears the highest burden, accounting for over 51% of global DALYs despite having less than 10% of the world’s population.
• Significant disparities exist between low and high SDI regions, highlighting health inequalities.

Gender and Age Group Differences

• Females exhibit higher incidence rates, while males have higher mortality and DALY rates across all age groups.
• The highest burden is concentrated in children under five years old, emphasizing the need for targeted interventions.

Inequality Analyses

• Absolute inequality in disease burden has decreased significantly from 1990 to 2021.
• Relative inequality remains high, indicating persistent disparities linked to socioeconomic status.
• Health inequalities align with SDG 10, underscoring the need to reduce disparities.

Natural Environment Index (NEI) and Interaction with SDI

• NEI, incorporating factors such as coastal area proportion and latitude, significantly influences disease burden.
• Low SDI and high NEI regions show greater sensitivity to environmental and socioeconomic factors, exacerbating disease burden.
• These findings highlight the intersection of SDG 13 (Climate Action) and SDG 3 in addressing health impacts of climate change.

Frontier Analysis

• Most countries have improved disease burden management from 1990 to 2021, approaching optimal governance frontiers.
• High NEI risk regions in low SDI countries show substantial governance potential, indicating opportunities for targeted interventions.

Projections (2022–2041)

• The global burden of NTDs and malaria is projected to increase, particularly in Middle and Low-middle SDI regions.
• High and High-middle SDI regions are expected to maintain lower burden levels due to better healthcare infrastructure.
• These projections emphasize the urgency of sustainable development efforts aligned with SDG 3 and SDG 13.

Discussion

1. Persistent Burden and Inequality: Despite progress, NTDs and malaria continue to impose a heavy burden, especially in children under five and in low-income tropical regions, reflecting challenges in achieving SDG 3.
2. Impact of Climate Change: Environmental factors and climate change exacerbate disease transmission, disproportionately affecting vulnerable populations, linking health outcomes to SDG 13.
3. Gender Disparities: Differences in incidence and mortality between males and females suggest the need for gender-sensitive health policies.
4. Health Inequalities: The concentration of disease burden in low SDI regions underscores the importance of SDG 10 in reducing inequalities.
5. Governance and Control Potential: Frontier analysis reveals opportunities for improving disease management, especially in high-risk, low-income countries.
6. Future Challenges: Projected increases in disease burden call for integrated, multi-sectoral strategies to meet SDG targets and promote global health equity.

Limitations

The study relies on GBD estimates, which may include biases and may not fully capture the actual global disease burden. Despite this, the findings provide valuable insights for policy and intervention planning.

Conclusions

• The overall burden of NTDs and malaria has declined but remains unequally distributed, with significant disparities between low- and high-income countries, particularly in Western Sub-Saharan Africa.
• Environmental and socioeconomic factors interact to influence disease burden, with climate change likely to worsen health outcomes in vulnerable regions.
• Future disease burden is expected to rise, especially in Middle and Low-middle SDI regions, necessitating enhanced efforts aligned with the Sustainable Development Goals.
• Addressing these challenges requires coordinated global action focusing on health equity (SDG 3), poverty reduction (SDG 1), inequality reduction (SDG 10), and climate action (SDG 13).

Data Availability

All data used in this report were obtained from the publicly accessible Global Burden of Disease (GBD) database, available at https://ghdx.healthdata.org/gbd-2021. Statistical analyses were conducted using R version 4.4.1.

1. Sustainable Development Goals (SDGs) Addressed or Connected

1. SDG 3: Good Health and Well-being
   • The article focuses on reducing the burden of Neglected Tropical Diseases (NTDs) and malaria, which directly relates to ensuring healthy lives and promoting well-being for all ages.
   • It discusses disease incidence, mortality, and Disability-Adjusted Life Years (DALYs), which are core health indicators.
2. SDG 1: No Poverty
   • The article highlights that NTDs and malaria disproportionately affect low-income and tropical poverty-stricken countries, indicating a link to poverty reduction.
   • It mentions the vicious cycle of poverty and disease burden.
3. SDG 10: Reduced Inequalities
   • The article analyzes health inequalities and disparities in disease burden between low-income and high-income countries, emphasizing the need to reduce inequalities.
4. SDG 13: Climate Action
   • The article discusses the impact of climate change and environmental factors on the burden of NTDs and malaria, highlighting the need for climate action to mitigate health impacts.

2. Specific Targets Under Identified SDGs

1. SDG 3: Good Health and Well-being
   • Target 3.3: By 2030, end the epidemics of AIDS, tuberculosis, malaria, and neglected tropical diseases and combat hepatitis, water-borne diseases, and other communicable diseases.
   • Target 3.8: Achieve universal health coverage, including access to quality essential health-care services and access to safe, effective, quality, and affordable essential medicines and vaccines.
2. SDG 1: No Poverty
   • Target 1.4: Ensure that all men and women, in particular the poor and vulnerable, have equal rights to economic resources and access to basic services.
3. SDG 10: Reduced Inequalities
   • Target 10.2: Empower and promote the social, economic, and political inclusion of all, irrespective of age, sex, disability, race, ethnicity, origin, religion, or economic or other status.
4. SDG 13: Climate Action
   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.

3. Indicators Mentioned or Implied to Measure Progress

1. Incidence Rate of NTDs and Malaria
   • Age-Standardized Incidence Rate (ASIR) per 100,000 population is used to measure new cases over time and across regions.
2. Mortality Rate
   • Age-Standardized Mortality Rate (ASMR) per 100,000 population is used to track deaths caused by NTDs and malaria.
3. Disability-Adjusted Life Years (DALYs)
   • Age-Standardized Disability-Adjusted Life Years Rate (ASDR) per 100,000 population measures overall disease burden combining mortality and morbidity.
4. Health Inequality Measures
   • Slope Index of Inequality (SII) and Concentration Index (CI) are used to assess absolute and relative inequalities in disease burden across socio-demographic indices.
5. Socio-Demographic Index (SDI)
   • Composite index of fertility rate, education, and income used to classify countries and analyze burden disparities.
6. Natural Environment Index (NEI)
   • Composite indicator quantifying environmental factors like temperature, rainfall, elevation impacting disease burden.
7. Forecasting Indicators
   • Bayesian Age-Prior-Cohort (BAPC) model projections of DALYs to predict future burden trends.

4. Table of SDGs, Targets, and Indicators

Source: nature.com