Short-term exposure to most major air pollutants associated with increased risk of heart attack

February 14, 2012

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, according to a review and meta-analysis of previous studies appearing in the February 15 issue of JAMA.

The potentially harmful effect of episodes of high air pollution on health has been suspected for more than 50 years. "In , 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 and human health in terms of and overall mortality, including respiratory or . However, the association between air pollution and near-term risk of [MI; ] remains controversial. Some studies have shown an association, while other studies have found either no association or association only for selected pollutants," according to background information in the article.

Hazrije Mustafic, M.D., M.P.H., of the University Paris Descartes, INSERM Unit 970, Paris, and colleagues conducted a systematic review and meta-analysis to examine the association between short-term exposure to air pollutants and the , and to quantify these associations. The major air pollutants included in the analysis were ozone, carbon monoxide, , , and particulate matter (PM) with an aerodynamic diameter of 10 μm (micrometers; PM10) or less and those 2.5 micrometers (PM2.5) or less.

The researchers conducted a search of the medical literature and identified 34 studies that met criteria for inclusion in the analysis, which indicated associations of statistical significance between all analyzed air pollutants and heart attack risk, with the exception of ozone. The subgroup analysis, based on study quality, yielded results comparable with those from the overall analysis.

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."

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."

"In conclusion, our meta-analysis is the first to our knowledge to evaluate the quality and magnitude of associations between short-term exposure to major air pollutants and the risk of MI," the authors write. "Further research is needed to determine whether effective interventions that improve air quality are associated with a decreased incidence of MI."

Explore further: High pollution levels linked to increase in heart attack risk

More information: JAMA. 2012;307[7]:713-721.

Related Stories

High pollution levels linked to increase in heart attack risk

September 20, 2011
High levels of pollution could increase the risk of having a heart attack for up to six hours after exposure, finds research published in the British Medical Journal today.

Study finds association between air pollution and cognitive decline in women

February 13, 2012
A large, prospective study led by a researcher at Rush University Medical Center indicates that chronic exposure to particulate air pollution may accelerate cognitive decline in older adults. The results of the study will ...

Recommended for you

One in 4 women and 1 in 6 men aged 65+ will be physically disabled in Europe by 2047

October 23, 2017
By 2047 one in four women and one in six men aged 65 and above is expected to be living with a physical disability that will severely restrict everyday activities, reveals an analysis published in the online journal BMJ Open.

Protein regulates vitamin A metabolic pathways, prevents inflammation

October 23, 2017
A team of researchers from Case Western Reserve University School of Medicine have discovered how uncontrolled vitamin A metabolism in the gut can cause harmful inflammation. The discovery links diet to inflammatory diseases, ...

New insights into controversial diagnosis of adolescent chronic fatigue

October 23, 2017
Crucial new research could provide some clarity around the controversy surrounding the diagnosis and treatment of chronic fatigue syndrome (CFS) in adolescents. The research by the Murdoch Children's Research Institute published ...

Do boys really have a testosterone spurt at age four?

October 23, 2017
The idea that four-year-old boys have a spurt of testosterone is often used to explain challenging behaviour at this age.

Our laws don't do enough to protect our health data

October 23, 2017
Have you ever wondered why your computer often shows you ads that seem tailor-made for your interests? The answer is big data. By combing through extremely large datasets, analysts can reveal patterns in your behavior.

New prevention exercise programme to reduce rugby injuries

October 23, 2017
A new dynamic 20-minute exercise programme, performed by rugby players before training and pre-match, could dramatically reduce injuries in the sport according to a benchmark study published today (Sunday 22 October).

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.