Air pollution linked to high blood pressure in children; other studies address air quality and the heart

Research Highlights:

• A meta-analysis of 14 air pollution studies from around the world found that exposure to high levels of air pollutants during childhood increases the likelihood of high blood pressure in children and adolescents, and the risk of hypertension later in life.
• A special publication on air pollution features several studies focused on the relationship between ambient air pollution with cardiovascular risk factors such as hypertension.
• Other studies cover exposure to diesel exhaust, ambient air pollution and particulate matter and how it affects blood pressure, heart failure admissions and risk of stroke and heart attack.
• Across the studies, researchers assessed the health outcomes of people who were exposed to pollutants in the United States, China and Europe. 

Embargoed until 4 a.m. CT/5 a.m. ET Tuesday, May 4, 2021                                                                                                                   

DALLAS, May 4, 2021 — A meta-analysis of 14 air pollution studies from around the world found that exposure to high levels of air pollutants during childhood increases the likelihood of high blood pressure in children and adolescents, and their risk for high blood pressure as adults. The study is published in a special issue on air pollution in the Journal of the American Heart Association, an open access journal of the American Heart Association.

Other studies look at: the effects of diesel exhaust on the muscle sympathetic nerve; the impact of pollutants on high blood pressure; rates of hospital readmission for heart failure among those exposed to high levels of ambient air pollution; and risk of stroke and heart attack after long-term exposure to high levels of particulate matter. The studies include health outcomes of people who were exposed to pollutants in the United States, China and Europe.

High blood pressure during childhood and adolescence is a risk factor for hypertension and heart disease in adulthood. Studies on air pollution and blood pressure in adolescents and children, however, have produced inconsistent conclusions. This systematic review and meta-analysis pooled information from 14 studies focused on the association between air pollution and blood pressure in youth. The large analysis included data for more than 350,000 children and adolescents (mean ages 5.4 to 12.7 years of age).

“Our analysis is the first to closely examine previous research to assess both the quality and magnitude of the associations between air pollution and blood pressure values among children and adolescents,” said lead study author Yao Lu, M.D., Ph.D., professor of the Clinical Research Center at the Third Xiangya Hospital at Central South University in Changsha, China, and professor in the department of life science and medicine at King’s College London. “The findings provide evidence of a positive association between short- and long-term exposure to certain environmental air pollutants and blood pressure in children and adolescents.”

The analysis included 14 studies published through September 6, 2020, exploring the impact of long-term exposure (≥30 days) and/or short-term exposure (<30 days) of ambient air pollution on blood pressure levels of adolescents and/or children in China and/or countries in Europe.

The studies were divided into groups based upon length of exposure to air pollution and by composition of air pollutants, specifically nitrogen dioxide and particulate matter with diameter ≤10 μm or ≤2.5 μm. (The majority of research linking heart disease with particulate matter focuses on particle matter mass, which is categorized by aerodynamic diameter – μm or PM.) Fine particles are defined as PM_2.5 and larger; coarse particles are defined at PM₁₀; and the concentrations of particulate matter are typically measured in their mass per volume of air (μg/m³).

The meta-analysis concluded:

• Short-term exposure to PM₁₀ was significantly associated with elevated systolic blood pressure in youth (the top number on a blood pressure reading).
• Periods of long-term exposure to PM_2.5, PM₁₀ and nitrogen dioxide were also associated with elevated systolic blood pressure levels.
• Higher diastolic blood pressure levels (the bottom number on a blood pressure reading) were associated with long-term exposure to PM_2.5 and PM₁₀.

“To reduce the impact of environmental pollution on blood pressure in children and adolescents, efforts should be made to reduce their exposure to environmental pollutants,” said Lu. “Additionally, it is also very important to routinely measure blood pressure in children and adolescents, which can help us identify individuals with elevated blood pressure early.”

The results of the analysis are limited to the studies included, and they did not include data on possible interactions between different pollutants, therefore, the results are not generalizable to all populations. Additionally, the analysis included the most common and more widely studied pollutants vs. air pollutants confirmed to have heart health impact, of which there are fewer studies.

The study was funded by the National Natural Science Foundation of China; Hunan Youth Talent Project; the Natural Science Foundation of Hunan Province; and the Fundamental Research Funds for Central Universities of Central South University.

Co-authors of the meta-analysis are Miao Huang, M.D.; Jingyuan Chen, M.D.; Yiping Yang, B.M.; Hong Yuan, M.D., Ph.D.; and Zhijun Huang, M.D. Author disclosures are listed in the manuscript.

Additional original articles published in JAHA’s spotlight on air pollution include:

• Acute exposure to diesel exhaust increases muscle sympathetic nerve activity in humans, Bosson et al.
• Short-term Effects of Particle Size and Constituents on Blood Pressure in Healthy Young Adults in Guangzhou, China, Dong et al.
• Lead and Cadmium as Cardiovascular Risk Factors: Has the Burden of Proof Been Met?, Lamas et al.
• Particulate air pollution and risk of cardiovascular events among adults with a history of stroke or acute myocardial infarction, Liao et al.
• Long-term Exposure to Particulate Air Pollution is Associated with 30-day Readmissions and Hospital Visits Among Heart Failure Patients, Ward-Caviness et al.

Additional Resources:

Statements and conclusions of studies published in the American Heart Association’s scientific journals are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers are available here, and the Association’s overall financial information is available here. 

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