Cardiovascular risk: the effect of pollution confirmed

Several studies presented at the meeting of the American Heart Association (AHA) to New Orleans (United States) support the hypothesis of an adverse effect of air pollution on the risk of cardiovascular disease.

Pollution also affects the heart ...

While scientists were especially interested in the link between pollution and lung disease, the data accumulated to show that the heart is also affected.

At a conference of the AHA, a team of Dijon had demonstrated a link between the peaks of air pollution and an increased risk of heart attack in the next few hours. This effect was visible especially in smokers and the risk was primarily associated with microparticles related to automobile pollution.

Then came the French researchers who presented results on pollution and acute coronary event risk in objectifying this time an association with ozone.

Dr. Vanina Bongard and colleagues at Toulouse University conducted a study on the city where the automobile pollution remains relatively moderate but where, due to sunlight, ozone concentrations can be high.

The researchers identified 635 cases of acute coronary events occurred in persons 55 to 64 years, for a period of two and a half years. They then attempted to correlate the time of occurrence of these events and the levels of certain pollutants measured continuously by a weather station in the Toulouse area.

They found an increased risk in the elevations of the ozone concentration in the air. In fact, for each increase of 5 microg/m3 ozone in the atmosphere, the risk of acute coronary event was increased by 5% on the same day and the next day.

The risk seemed also higher among people with no history of cardiovascular disease, for which each increase of 5 microg/m3 ozone increased the risk by 14%.

"It is possible that patients with cardiovascular disease are protected from the effects of ozone pollution due to medical treatment they follow," suggests Dr. Bongard.

In contrast, the risk of cardiovascular complications was not associated with concentrations of nitrogen dioxide and sulfur, but these were much lower, she observes.

To explain the link pollution / risk coronary two hypotheses

Asked by Reuters Health on the mechanism by which ozone increase acute coronary risk, specialist offers two possibilities: either a direct effect of ozone induce vasoconstriction or an indirect effect through an inflammatory mechanism.

However, she warns, the risk of pollution is not only coronary. Indeed, a study in Israel also objective association between pollution and the risk of acute heart failure.

Dr. Gad Cotter of Duke University in Durham (United States) and his Israeli colleagues studied 300 patients with acute heart failure during a period of 4 months in hospital Zerifin.

The researchers found that on days when the air concentration of particles proved high, the average number of admissions for heart failure became significantly higher: 3.2 against 2.2 events events when the concentration of the pollutant was lower.

According to Dr. Cotter, inflammatory phenomena are probably involved to explain the effect of particulate pollution on cardiac risk.

These studies have linked various forms of air pollution and the risk of acute cardiac events. But a third study suggests that pollution may have a chronic effect on the cardiovascular system.

In fact, Dr. Nino Kuenzli University of Los Angeles (USA) examined the effect of pollution on the development of atherosclerosis.

Studies in rabbits have shown that exposure to microparticles leads to the development of atherosclerosis. Californian researchers have verified this result in humans.

They studied 798 people who underwent measurement of the intima-media thickness in the carotid artery (the vessel neck) to estimate the degree of atherosclerosis of the entire circulatory system . Participants were then classified into different groups according to the degree of pollution by microparticles.

It turns out as well as the level of exposure to pollutants was correlated with the importance of atherosclerosis assessed at the carotid artery. For each increase of 10 microg/m3 density microparticles, the intima-media thickness was increased by 5.9%.

After taking into account other factors, including socio-demographic and lifestyle related, increasing the thickness of the intima-media with increasing microparticles from 3.9% to 4.3 %.

This effect was greater in postmenopausal women and people under lipid-lowering therapy.

"These results show an association between air pollution and subclinical atherosclerosis," says the researcher, noting that this effect appears to be similar to that of passive smoking.

Adding carefully that this work should be confirmed, it nevertheless considers this disturbing result since "exposure to pollution begins at birth and continues throughout life." Pollution could therefore significantly contribute to the epidemiology of cardiovascular disease.

Produced and validated in collaboration with healthcare professionals

under the direction of Dr. Anne Richard