Clean air protects children from high blood pressure and elevated diabetes markers
Reduced levels of the air pollutants black carbon and particulate matter (PM2.5) improve insulin and glucose metabolism and reduce the risk of developing high blood pressure in children and adolescents.
Observational studies have long indicated that polluted air promotes inflammatory processes in the body and impairs glucose metabolism and the cardiovascular system, which increase the risk of type 2 diabetes and high blood pressure. However, associations seen in observational studies are 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. In environmental 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 at BIPS, 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 Bornhorst, statistician at BIPS.
The results are clear: reduced levels of the air pollutants black carbon and particulate matter (PM2.5) improve insulin and glucose metabolism and reduce the risk of developing high blood pressure in children and adolescents. The studies thus provide strong evidence of a direct, causal link between 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 PM2.5 would substantially reduce the risk of high blood pressure and elevation in diabetes markers in children. Given that the WHO's global air quality guidelines 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 hypothetical black carbon limits and estimating their potential health benefits for children.
The IDEFICS/I.Family cohort as a scientific basis
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 two and ten 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. A clean environment is therefore a key factor in the long-term prevention of chronic diseases such as diabetes and hypertension," said Rajini Nagrani. "We hope that policy makers may be motivated by our results to ensure adherence to recommended levels of air pollutants," added Maike Wolters.
Original publications
Rajini Nagrani, Maike Wolters, Christoph Buck, Danielle Vienneau, Kees deHoogh, Stefaan De Henauw, Lauren Lissner, Denes Molnar, Luis Moreno, Marika Dello Russo, Valeria Pala, Wolfgang Ahrens, Vanessa Didelez, Claudia Bornhorst: Effect of long-term air pollution reduction on insulin resistance and fasting glucose in children: A causal analysis. Environmental Research 2025, 122920, ISSN 0013-9351, https://doi.org/10.1016/j.envres.2025.122920
Maike Wolters, Rajini Nagrani, Nour Naaouf, Stefaan De Henauw, Lauren Lissner, Luis A. Moreno, Denes Molnar, Paola Russo, Tanja Vrijkotte, Wolfgang Ahrens, Claudia Bornhorst on behalf of the IDEFICS/I.Family consortium: Effects of ambient air pollutants and environmental greenness on the incidence of pre/hypertension in children and adolescents. European Journal of Preventive Cardiology 2025, zwaf600, https://doi.org/10.1093/eurjpc/zwaf600
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