Short-term exposure (for up to 7 days) to all major air pollutants, with the exception of ozone, is significantly associated with an increased risk of heart attack.
The connection between pollution and heart attacks is based on a review and meta-analysis of previous studies appearing in the February 15 issue of JAMA.
Heart Health and Air Pollution
The potentially harmful effect of episodes of high air pollution on health has been suspected for more than 50 years. “In industrialized countries, cardiovascular disease is the leading cause of mortality and is associated with significant morbidity. These countries have high pollution levels. Since the 1990s, many epidemiological studies have demonstrated associations between air pollution levels and human health in terms of hospital admissions and overall mortality, including respiratory or cardiovascular mortality.” the study notes.
Risk of Heart Attack Reviewed
Hazrije Mustafic, M.D., M.P.H., of the Paris Cardiovascular Research Center, University Paris Descartes, and colleagues conducted a systematic review and meta-analysis to examine the association between short-term exposure to air pollutants and the risk of heart attack, and to quantify these associations.
The major air pollutants included in the analysis were ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter (PM).
How the Heart is Impacted by Pollution
The authors suggest a number of possible mechanisms for the associations found.
“The first potential mechanism is inflammation. Studies have shown that levels of inflammatory markers such as C-reactive protein are higher as a result of exposure to air pollution.
The second potential mechanism is abnormal regulation of the cardiac autonomic system. Several observational studies have linked high levels of air pollution with increased heart rate and decreased heart rate variability.
The third possible mechanism is an increase in blood viscosity as a result of air pollution. This association can promote thrombus [blood clot] formation, accelerate the progression of atherosclerosis, and weaken the stability of atherosclerotic plaques.”
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Improving Air Quality for Better Public Health
The researchers acknowledge that the magnitude of association found in this study is relatively small compared with those of classic heart attack risk factors, such as smoking, hypertension, or diabetes.
“Nevertheless, the population attributable fractions of each pollutant is not negligible because the majority of the population, including young and disabled patients, is exposed to air pollution, particularly in urban settings, and thus an improvement in air quality could have a significant effect on public health.”
JAMA. 2012;307(7):713-721. doi: 10.1001/jama.2012.126 “Main Air Pollutants and Myocardial Infarction A Systematic Review and Meta-analysis”, Hazrije Mustafić, MD, MPH et al.