by Rasmus Cloes, Leibniz-Institut für Präventionsforschung und Epidemiologie

Credit:European Journal of Preventive Cardiology(2025). DOI: 10.1093/eurjpc/zwaf600

Two new studies by the Leibniz Institute for Prevention Research and Epidemiology–BIPS in Bremen show for the first time that air quality directly influences blood pressure (pre-hypertension and hypertension) and important markers for diabetes risk in children and adolescents. These findings were made possible by the use of causal inference methods to determine the effects of hypothetical interventions.

The studies are published inEnvironmental Researchand theEuropean Journal of Preventive Cardiology.

Observational studies have long indicated that polluted air promotes inflammatory processes in the body and impairs glucose metabolism and the cardiovascular system, which increases the risk of type 2 diabetes and highblood pressure. However, associations seen inobservational studiesare not necessarily causal.

Randomized controlled studies would seemingly be the right approach to provide strong support for causality. Here, individuals are randomly assigned to two groups that would be exposed to different levels of air pollution under defined conditions. Inenvironmental health, however, such studies are virtually impossible to carry out: they would not only be extremely expensive and logistically complex, but above all ethically unacceptable.

That is why the BIPS team led by Dr. Rajini Nagrani, head of the Molecular Epidemiology unit, and by Dr. Maike Wolters, senior scientist in the Behavior and Health unit, chose an innovative approach. Based on the IDEFICS/I.Family cohort, one of the largest European studies on children's health and lifestyle, they used hypothetical interventions to simulate the effect of improved air quality.

"In our study, we followed a principle called 'target trial emulation.' First, we specified an ideal randomized trial that could answer our research question of interest. In a second step, we emulated this ideal trial as close as possible based on observational data of a large children cohort. This approach allows us to estimate the possible causal effect without actually exposing children to risk," explains Dr. Claudia Börnhorst, statistician at BIPS.

The results are clear: Reduced levels of the air pollutants black carbon and particulate matter (PM2.5) improve insulin andglucose metabolismand reduce the risk of developing high blood pressure in children and adolescents.

The studies thus provide strong evidence of a direct,causal linkbetween air pollution and sugar metabolism disorders and high blood pressure in childhood. They also provide new arguments for measures to improve air quality, including to prevent diabetes and hypertension.

In most European regions, air pollution levels exceed cut-offs recommended by the WHO. BIPS's studies show that achieving the WHO targets for PM2.5would substantially reduce the risk ofhigh blood pressureand elevation in diabetes markers in children.

Given that the WHO's globalair qualityguidelines for 2021 do not include limits for black carbon due to a lack of data, the findings expand the evidence base for establishing black carbon limits by evaluating hypotheticalblack carbonlimits and estimating their potential health benefits for children.

The IDEFICS study and its extension, the I.Family study, are among the most comprehensive European studies on child health. Between 2007 and 2014, 16,230 children aged between 2 and 10 were examined repeatedly in eight European countries. Nutrition, physical activity, body measurements such as blood pressure, and blood and urine samples were recorded under standardized conditions.

For the current analysis, the BIPS team used longitudinal data from the IDEFICS/I.Family surveys to better understand the links between environmental factors and biological markers in childhood.

"Our studies provide important scientific evidence that air pollution control protects both the metabolism and the cardiovascular system. Aclean environmentis therefore a key factor in the long-term prevention of chronic diseases such as diabetes and hypertension," said Dr. Nagrani.

"We hope thatpolicy makersmay be motivated by our results to ensure adherence to recommended levels of air pollutants," added Dr. Wolters.

More information: Rajini Nagrani et al, Effect of long-term air pollution reduction on insulin resistance and fasting glucose in children: A causal analysis, Environmental Research (2025). DOI: 10.1016/j.envres.2025.122920 Maike Wolters et al, Effects of ambient air pollutants and environmental greenness on the incidence of pre-/hypertension in children and adolescents, European Journal of Preventive Cardiology (2025). DOI: 10.1093/eurjpc/zwaf600 Journal information: European Journal of Preventive Cardiology , Environmental Research

Provided by
Leibniz-Institut für Präventionsforschung und Epidemiologie