Temporal association between air pollution and myocardial infarctions

January 01, 0001

Temporal association between air pollution and myocardial infarctions

This group of British investigators examined the short term interactions between air pollution levels and risk of myocardial infarction (MI). They performed a time stratified case crossover study linking data on an hourly basis from the Myocardial Ischaemia National Audit Project (MINAP, 79 288 myocardial infarctions included in this study) with particulate of 10 micrometers diameter or less (PM10), ozone, CO, NO2, and SO2 data from the UK National Air Quality Archive. Single and multi-pollutant models were used and adjustments were made for other conditions such as temperature, humidity, infectious diseases, etc.

The researchers found: "In single pollutant models, PM10 and NO2 levels were associated with a very short term increase in risk of myocardial infarction 1-6 hours later (excess risks 1.2% and 1.1% respectively per 10 ìg/m3 increase). The effects persisted in multi-pollutant models, though with only weak evidence of an independent PM10 effect. The immediate risk increases were followed by reductions in risk at longer lags: we found no evidence of any net excess risk associated with the five pollutants studied over a 72 hour period after exposure."

The researchers concluded: "Higher levels of PM10 and NO2, which are typically markers of traffic related pollution, seem to be associated with transiently increased risk of myocardial infarction 1-6 hours after exposure, but later reductions in risk suggest that air pollution may be associated with bringing events forward in time ("short-term displacement") rather than increasing overall risk. The well established effect of air pollution on cardiorespiratory mortality may not be mediated through increasing the acute risk of myocardial infarction, but through another mechanism."

Small particulates and nitrous oxide air pollution are linked with a short term increase in myocardial infarction risk, but it appears to be associated with an earlier occurrence of infarction rather than increased overall risk

For the full abstract, click here.

BMJ 343:d5531, 20 September 2011 © 2011 BMJ Publishing Group Ltd.
The effects of hourly differences in air pollution on the risk of myocardial infarction: case crossover analysis of the MINAP database. Krishnan Bhaskaran, Shakoor Hajat, Ben Armstrong, et al.. Correspondence to K Bhaskaran: krishnan.bhaskaran@lshtm.ac.uk

Category: K. Circulatory. Keywords: myocardial infarction, air pollution, particulates, nitrous oxide, short term, case crossover study, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 14 October 2011

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