Air pollution is responsible for the sharp rise in deaths among patients who have been admitted to hospital with heart attacks, according to a new study.
The largest study yet to investigate the links between fine air-borne particulate matter (PM) and patient survival after hospital admission for acute coronary syndrome (ACS) found death rates increased with increased exposure to PM2.5 - tiny particles that measure 2.5 micrometers (um) in diameter or less, approximately 30 times smaller than a human hair.
The amount of PM in the air is measured as micrograms per cubic meter of air (ug/m3). The main sources of PM2.5 in the UK are emissions from road traffic and industry, including power generation.
Dr Cathryn Tonne, lecturer in environmental epidemiology at the London School of Hygiene and Tropical Medicine (London, UK) said: "We found that for every 10ug/m3 increase in PM2.5 there was a 20 percent increase in the death rate. For example, over one year of follow-up after patients had been admitted to hospital with ACS, there would be 20 percent more deaths among patients exposed to PM2.5 levels of 20 ug/m3, compared to patients exposed to PM2.5 levels of 10ug/m3."
Dr Tonne and her colleague Paul Wilkinson, professor of environmental epidemiology at the London School of Hygiene and Tropical Medicine, estimate that death rates would be reduced by 12 percent among ACS patients if they were exposed to naturally occurring PM2.5 rather than the higher levels they were actually exposed to. This translates to 4,783 deaths occurring earlier than they should do, due to exposure to PM2.5 from man-made sources.
The researchers linked records of 154,204 patients who survived hospital admission for ACS in England and Wales between 2004-2007 with modelled average air pollution concentrations for 2004-2010. The patients were followed up until the end of the study in April 2010 or their death, whichever occurred earlier. During the average follow-up time of 3.7 years, there were 39,863 deaths. The researchers adjusted their results to take account of the patients' sex, age, medical history, treatments and drugs, whether or not they smoked, socioeconomic factors such as income, education and employment, and where they lived.
The study was recently published in the European Heart Journal. (ANI)