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PostPosted: 12 Nov 2018 21:50 
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Air pollution is linked to changes in the structure of the heart of the sort seen in early stages of heart failure, say researchers. The finding could help explain the increased number of deaths seen in areas with high levels of dirty air. A report last year revealed that people in the UK are 64 times more likely to die from the effect of air pollution than people living in Sweden. Such premature deaths can be linked to a number of causes including respiratory problems, stroke and coronary artery disease.

“What we don’t know is what is the mechanism behind it, why is air pollution leading to increased risk of heart attack and stroke?” said Dr Nay Aung, a cardiologist at Queen Mary University of London and first author of the research.
Writing in the journal Circulation, Aung and colleagues report that they found exposure to nitrogen dioxide and fine particulate matter, known as PM2.5 and PM10 particles, is linked to an increase in the size of two of the chambers of the heart, the left and right ventricle. PM particles are commonly emitted by motor vehicles, among other sources.
The authors add that similar changes can affect the performance of the heart and are often seen before heart failure takes hold.

The team used data from almost 4,000 volunteers who were part of a wider research effort known as the UK Biobank. These participants were aged between 40 and 69 years old, had been at the same address for the whole study, and were free from cardiovascular disease at the outset. Crucially, their data included cardiac MRI scans, which offer detailed images of the structure and function of the heart.

The study also involved estimates of the outdoor concentrations of different pollutants at participants’ home addresses at about five years prior to the scan. After controlling for factors including age, sex, income and smoking history, the team found that higher exposure to PM2.5 particles, PM10 particles and nitrogen dioxide were each linked to a greater volume of both the right and left ventricles after they had filled with blood.

Aung said the size of the effect identified was small, but important. “This effect size is comparable to other well known cardiac risk factors such as hypertension,” he said, noting that as blood pressure rises the heart size increases. “Although the increase in heart chamber size is small in this study, it is an early warning sign, which may explain the increased risk of heart failure in individuals exposed to higher level of pollution.”

Aung said the study found that an increase in exposure to PM2.5 of 1µg/m3 was linked to an increase in the size of each ventricle of just under 1%. He stressed that the findings were of particular concern because most of the participants lived in areas with relatively low exposure to air pollution. On average, the participants were exposed to average PM2.5 concentrations of 8-12µg per cubic metre, close to the WHO recommended limit of 10µg/m3, but well within the UK guidelines of 25µg/m3. Research last year found that in some polluted areas such as central London, average levels of PM2.5 were above 18µg/ m3, with even higher levels seen on bad pollution days.

Kevin McConway, emeritus professor of Applied Statistics at the Open University, welcomed the study. “I think the study provides pretty convincing evidence of a correlation between levels of two air pollutants – fine particulates in the air and nitrogen dioxide – and measurable changes in the heart,” he said. But, he added, the study only shows a link, rather than showing that it is air pollution that is driving the heart changes. “In this study the researchers did adjust their results carefully to allow for possible effects of many factors to do with lifestyle,” he said. “Such statistical adjustments can never be perfect, though, so some doubt must remain about whether the heart changes are actually caused by the pollution.”

(2.5 (PM2.5), refers to tiny particles or droplets in the air that are two and one half microns or less in width. PM10 is particulate matter 10 micrometers or less in diameter,

Based on an article by Nicola Davis of The Guardian

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