The researchers from the London School of Hygiene & Tropical Medicine found that there was no clear evidence on the impact of pollution on directly boosting the risk of heart attacks and stroke, but the strongest associations with air pollution were observed with irregular heartbeat.
The team conducted a large national study looking into acute air pollution effects on cardiovascular diseases over a period of 2003 to 2009 in England and Wales. They looked at records of more than 400,000 heart attacks, two million emergency admissions for cardiovascular problems, and 600,000 deaths from cardiovascular diseases, and studied daily average levels of air pollutants using data from monitoring stations nearest to the place of residence. Investigated pollutants included carbon monoxide, nitrogen dioxide, particulate matter, sulphur dioxide, and ozone.
Dr Ai Milojevic from the London School of Hygiene & Tropical Medicine said: “Our findings show that air pollution is linked with irregular heartbeat, but not clearly linked with severe heart attack and stroke. What is particularly important is that we found the strongest links in the elderly and in hospital patients with chronic heart disease or irregular heart beat. Now we know that these groups are at an increased risk, this latest work could help inform intervention strategies to protect more vulnerable groups.”
No clear link with any air pollutant was found for cardiovascular deaths, with the exception of particulate matter smaller than 2.5 micrometers (PM2.5) which was linked to an increased risk of irregular heartbeat and blood clots in the lungs.
Only nitrogen dioxide was linked to an increased risk of emergency hospital admissions for cardiovascular problems, including irregular heartbeat, heart failure, and an increased risk of a particular type of heart attack (non-ST elevation myocardial infarctions).
The findings prompt the researchers to conclude that there is no clear evidence that short term exposure to air pollution boosts the risk of severe heart attacks (ST elevation myocardial infarctions) and stroke.
The authors note that limitations of their study include an overlap of some data from hospital admissions and heart attack events, the use of exposure level at fixed monitoring sites and that PM2.5 results may represent only urban areas due to limitations of the monitoring network in the UK.
Ai Milojevic, Paul Wilkinson, Ben Armstrong, Krishnan Bhaskaran, Liam Smeeth, Shakoor Hajat. Short-term effects of air pollution on a range of cardiovascular events in England and Wales: case-crossover analysis of the MINAP database, hospital admissions and mortality. Heart. DOI: 10.1136/heartjnl-2013-304963.
Image: Hazy London skyline due to air pollution. Credit: Flickr/Ben Sutherland
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