and ozone with global disease burden of Alzheimer’s disease and other dementias – Nature

 

Report on the Global Disease Burden of Dementia: The Interplay of Air Pollution, Greenness, and Sustainable Development Goals

Executive Summary

This report details the findings of an ecological study across 162 countries investigating the relationship between air pollutants (particulate matter PM_2.5 and ozone) and the disease burden of Alzheimer’s Disease (AD) and other dementias. The study critically examines the modifying role of environmental greenness, framing the results within the context of the United Nations Sustainable Development Goals (SDGs). The findings reveal a significant positive association between exposure to PM_2.5 and ozone and an increased burden of dementia, a critical challenge to SDG 3 (Good Health and Well-being). This association is disproportionately stronger in nations with lower socio-economic status, highlighting a clear link to SDG 10 (Reduced Inequalities). Crucially, the study demonstrates that higher levels of greenness can mitigate the harmful effects of these pollutants. This underscores the importance of integrated policy actions that advance SDG 11 (Sustainable Cities and Communities) and SDG 15 (Life on Land) as a direct public health strategy to protect neurological health and promote sustainable development.

Introduction: The Global Context of Dementia and Environmental Factors

The Rising Burden of Dementia and SDG 3

Alzheimer’s disease and other dementias represent a escalating global health crisis, identified as the seventh leading cause of death worldwide. With over 55 million people affected and projections rising to 139 million by 2050, the associated economic costs are expected to surpass US$ 2.8 trillion by 2030. This growing prevalence poses a significant obstacle to achieving SDG 3 (Good Health and Well-being), particularly Target 3.4, which aims to reduce premature mortality from non-communicable diseases. Identifying modifiable risk factors is therefore a global public health priority.

Environmental Risk Factors and the SDGs

Among the potentially modifiable risk factors for dementia, environmental factors are gaining recognition. This study focuses on two key environmental exposures:

• Air Pollution: Pollutants such as PM_2.5 and ozone are known to trigger neuroinflammation and oxidative stress. Addressing air quality is a core component of SDG 11.6, which calls for reducing the adverse per capita environmental impact of cities.
• Greenness: Natural environments are associated with improved cognitive function, potentially by reducing stress, promoting physical activity, and mitigating air pollution. The promotion of green spaces aligns with SDG 11.7 (universal access to safe and inclusive green spaces) and SDG 15 (Life on Land).

Study Objectives

This ecological study was conducted with two primary objectives:

1. To examine the association between PM_2.5 and ozone exposure and the global disease burden of AD and other dementias.
2. To assess the potential modifying effect of environmental greenness on this association.

Methodology

Study Design and Data Sources

An ecological study was performed using publicly available, country-level data from 162 nations for the years 2010, 2011, 2014, 2015, 2016, and 2017. Data were aggregated from the following sources:

• Dementia Burden Data: Incidence, death, and Disability-Adjusted Life Years (DALY) rates for AD and other dementias were sourced from the Global Health Data Exchange (GHDx).
• Air Pollutant Data: Population-weighted annual average concentrations of PM_2.5 and seasonal average ozone concentrations were also obtained from the GHDx.
• Greenness Data: Country-level greenness was quantified using satellite-derived Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) from the MODIS Terra satellite product.

Covariates and Statistical Analysis

A Generalized Linear Mixed Model (GLMM) was employed to analyze the associations, controlling for a range of country-level covariates, including demographic characteristics, socioeconomic variables (Socio-Demographic Index [SDI], Gross National Income [GNI]), medical services, and meteorological factors. To investigate the link with SDG 10 (Reduced Inequalities), stratified analyses were conducted based on country-level SDI and GNI. The modifying effect of greenness was assessed by stratifying the analysis by quantiles of NDVI.

Key Findings

The Detrimental Impact of Air Pollution on Neurological Health

The study confirmed a statistically significant detrimental association between air pollutants and the burden of dementia, posing a direct threat to achieving SDG 3. In the fully adjusted model:

• A 10-unit increment in PM_2.5 was associated with a 2.0% increase in incidence, a 2.8% increase in deaths, and a 2.2% increase in DALYs.
• A 10-unit increment in ozone was associated with a 1.9% increase in incidence, a 9.5% increase in deaths, and a 6.7% increase in DALYs.

Socioeconomic Disparities and SDG 10

The analysis revealed significant health inequalities. The harmful effects of both PM_2.5 and ozone on dementia burden were substantially more pronounced in countries with lower Socio-Demographic Index (SDI) and lower Gross National Income (GNI). This finding highlights that the environmental burden of disease is not distributed equally, reinforcing the urgency of addressing the targets within SDG 10 (Reduced Inequalities).

The Mitigating Role of Greenness: A Pathway to Sustainable Health

A critical finding of this report is the protective effect of green spaces. The analysis demonstrated that in countries with high levels of greenness (as measured by NDVI), the adverse association between air pollutants and dementia burden was significantly attenuated. For populations in the highest quartile of greenness exposure, the harmful effects of PM_2.5 and ozone were diminished, becoming statistically insignificant or even suggesting a protective effect. This provides strong evidence that investing in green infrastructure is a powerful public health intervention that supports the objectives of SDG 11 and SDG 15.

Discussion and Policy Implications for Sustainable Development

Integrating Environmental and Health Policies for the SDGs

This study provides compelling, global-level evidence that exposure to air pollution increases the risk of dementia, particularly in lower-income nations. Furthermore, it demonstrates that greenness can modify and reduce this risk. These findings call for an integrated policy approach that bridges environmental protection and public health to accelerate progress on the SDGs.

• Strengthen Air Quality Standards (SDG 3, SDG 11): Governments must prioritize the reduction of ambient PM_2.5 and ozone through stricter regulations and cleaner energy transitions. This is not only an environmental imperative but a crucial action to protect the neurological health of populations.
• Promote Urban Greening (SDG 11, SDG 15): Urban planning and public policy should actively promote the creation and preservation of green spaces. Investing in parks, urban forests, and vegetation cover is a cost-effective strategy to mitigate pollution, improve health outcomes, and create more resilient and sustainable communities.
• Address Health Inequalities (SDG 10): Interventions must be targeted toward vulnerable populations in low-income countries. International cooperation and financial support are needed to help these nations build capacity for monitoring air quality and implementing greening initiatives, thereby addressing the disproportionate health burdens they face.

In conclusion, tackling the global dementia crisis requires a multi-faceted approach that recognizes the profound impact of the environment on human health. By aligning public health strategies with the Sustainable Development Goals, particularly those related to air quality, green spaces, and inequality, nations can build a healthier and more sustainable future for all.

SDGs Addressed in the Article

The article discusses issues that are directly and indirectly connected to several Sustainable Development Goals. The analysis highlights the intricate relationships between environmental factors, health outcomes, urban living, and socioeconomic disparities.

• SDG 3: Good Health and Well-being

  This is the most prominent SDG in the article. The entire study revolves around understanding the health impacts of environmental factors on a specific non-communicable disease. It investigates the “disease burden of AD and other dementias,” including incidence, death, and disability-adjusted life years (DALY) rates, directly aligning with the goal of ensuring healthy lives and promoting well-being for all at all ages.

• SDG 11: Sustainable Cities and Communities

  The article addresses this goal by focusing on two key aspects of urban and community environments: air pollution and green spaces. It examines the negative effects of “air pollutants (PM_2.5 and ozone)” and the positive, mitigating effects of “greenness.” The study’s conclusion that increasing green spaces could cope with the adverse effects of air pollution is a direct recommendation for making human settlements more sustainable and healthy.

• SDG 10: Reduced Inequalities

  The study explicitly brings this goal into focus by analyzing how the health impacts of air pollution are distributed across different socioeconomic groups. The finding that the negative associations “were found to be more pronounced in countries with lower socio-demographic index and gross national income” highlights a significant inequality in health outcomes based on economic status, emphasizing the need to address environmental justice.

• SDG 15: Life on Land

  This goal is relevant through the article’s investigation of “greenness,” measured by the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). The study demonstrates the protective health benefits of terrestrial ecosystems (vegetation, forests, parks), showing that “higher levels of greenness exposure may have a modifying effect, mitigating the adverse impacts of air pollutants.” This underscores the value of conserving and restoring terrestrial ecosystems for human well-being.

Specific SDG Targets Identified

Based on the content of the article, several specific targets under the identified SDGs can be pinpointed.

1. Targets under SDG 3 (Good Health and Well-being)

   • Target 3.4: By 2030, reduce by one third premature mortality from non-communicable diseases through prevention and treatment and promote mental health and well-being.
     
     Explanation: The article focuses on Alzheimer’s disease and other dementias, which are non-communicable diseases. It analyzes the “death, and disability-adjusted life years (DALY) rate” associated with these conditions and investigates modifiable environmental risk factors (air pollution) and protective factors (greenness) as a means of prevention.
   • Target 3.9: By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.
     
     Explanation: The study’s primary objective is to examine the “detrimental association between PM_2.5 and ozone exposure and the disease burden of AD and other dementias.” It directly links air pollutants to increased rates of incidence, death, and DALYs, aligning perfectly with this target’s aim to reduce mortality and morbidity from air pollution.

2. Targets under SDG 11 (Sustainable Cities and Communities)

   • Target 11.6: By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality.
     
     Explanation: The research quantifies the health impact of poor air quality by measuring “population-weighted annual average mass concentration of PM_2.5” and ozone levels. This directly relates to the target of managing and reducing the negative effects of urban air quality.
   • Target 11.7: By 2030, provide universal access to safe, inclusive and accessible, green and public spaces.
     
     Explanation: The article provides strong evidence for this target by demonstrating that “in areas with high levels of greenness, both PM_2.5 and ozone were observed to be associated with a diminished risk of disease burden.” This supports the argument for increasing green spaces as a public health intervention.

3. Targets under SDG 10 (Reduced Inequalities)

   • Target 10.2: By 2030, empower and promote the social, economic and political inclusion of all, irrespective of… economic or other status.
     
     Explanation: The article highlights a clear disparity, stating that the disease burden from air pollution is “notably higher in low SDI countries” and “more pronounced in countries with low GNI.” This finding points to an inequality where populations in lower-income countries bear a disproportionately higher health burden from environmental hazards, which is a key concern of this target.

Implied or Mentioned Indicators

The article uses specific metrics and data points that align with or serve as proxies for official SDG indicators.

• Indicators for SDG 3 Targets

  • For Target 3.4 & 3.9 (Indicator 3.4.1 & 3.9.1): The article uses several direct and relevant metrics to measure mortality and disease burden. These include:
    • Mortality/Death Rate: The study calculates the “death rate… for AD and other dementias” and its association with air pollutants. This is a direct measure for the mortality component of these indicators.
    • Incidence Rate: The “increased risk of incidence” is analyzed, which measures the rate of new cases of illness from air pollution.
    • Disability-Adjusted Life Years (DALY) Rate: The use of DALYs is a comprehensive measure of overall disease burden, combining years of life lost due to premature mortality and years lived with disability, directly reflecting the “illnesses” and “premature mortality” aspects of the targets.

• Indicators for SDG 11 Targets

  • For Target 11.6 (Indicator 11.6.2): The article explicitly uses the core metric for this indicator:
    • Annual mean levels of fine particulate matter (PM_2.5): The study acquired and analyzed data on “population-weighted annual average mass concentration of PM_2.5.” It also included ozone concentrations, another key measure of air quality.
  • For Target 11.7 (Indicator 11.7.1): The study uses scientific proxies to measure green space coverage:
    • Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI): The article states, “We utilized country-level normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) data… to evaluate the greenness exposure.” These satellite-derived indices are quantitative measures of vegetation cover and serve as a proxy for the availability of green space.

• Indicators for SDG 10 Targets

  • For Target 10.2: The article uses established economic indicators to stratify its analysis and reveal inequalities:
    • Socio-demographic Index (SDI): The study “categorized the data into three groups: low, middle… and high SDI” to show differing impacts.
    • Gross National Income (GNI): The analysis was stratified by GNI, which “was dichotomized into low income… and high income” to demonstrate that the adverse health effects were more pronounced in low-income countries.

Summary Table of SDGs, Targets, and Indicators

SDGs	Targets	Indicators Mentioned or Implied in the Article
SDG 3: Good Health and Well-being	3.4: Reduce premature mortality from non-communicable diseases. 3.9: Reduce deaths and illnesses from air pollution.	Mortality rate from Alzheimer’s disease (AD) and other dementias. Incidence rate of AD and other dementias. Disability-Adjusted Life Years (DALY) rate due to AD and other dementias.
SDG 11: Sustainable Cities and Communities	11.6: Reduce the adverse environmental impact of cities, focusing on air quality. 11.7: Provide universal access to green and public spaces.	Population-weighted annual average concentration of PM2.5. Seasonal average eight-hour daily maximum concentration of ozone. Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) as measures of greenness.
SDG 10: Reduced Inequalities	10.2: Promote inclusion irrespective of economic status.	Socio-demographic Index (SDI) used to stratify health outcomes. Gross National Income (GNI) used to demonstrate disproportionate health burdens on low-income countries.
SDG 15: Life on Land	15.9: Integrate ecosystem values into national and local planning.	Quantification of the mitigating health effects of “greenness” (NDVI/EVI), demonstrating the value of ecosystems in public health planning.

Source: nature.com