Researchers from London, reveal in a new study that air pollution adds to the increased numbers of deaths among heart attack patients hospital admittance.
This new study is the largest to date to examine the association between fine air-borne particle matter (PM) and patient survival after hospital admission due to acute coronary syndrome (ACS).
The goal for this study was to determine if long-term exposure to air pollution was linked with all-cause mortality.
The amount of PM in the air is measured as micrograms per cubic meter of air (μg/m3). The main sources of PM2.5 in the UK are emissions from road traffic and industry, including power generation.
Dr. Cathyrn Tonne, Sc.D, M.P.H., Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine and colleague Professor Paul Wilkinson, Center for Environment and Health, King's College London, had examined 154,204 records of patients admitted to hospital with acute coronary syndrome (ACS) in MINAP collected under the National Institute for Cardiovascular Outcomes Research were linked to modeled annual average air pollution concentrations for 2004–10. The patients were followed up until the end of the study in April 2010 or their death, whichever occurred earlier.
Among the 154 204 patients included in the cohort, the average follow-up was 3.7 years and 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 air pollution modeling of average exposures for different regions of the country showed the highest average exposures to PM2.5 and other air pollutants in London (an average of 14.1 µg/m3), while the North East of England had the lowest exposure (an average of 8.4 µg/m3). However, people’s individual exposure to PM2.5 varied widely within each region.
Evidence has been growing that exposure to air pollution is associated with the development of heart disease, but, so far, few studies have investigated its effect on survival after heart attacks (myocardial infarction) and the findings have been inconsistent.
In 2010, the American Heart Association expert review group examined dozens of studies over the previous six years that focused on fine particle pollution from traffic and industry. They had concluded there was enough evidence to link heart attacks to air pollution.
It has also been noted patients from poorer backgrounds often live in more deprived areas with higher levels of air pollution and that they tend to do less well after a diagnosis of heart problems than patients of a higher socioeconomic status. "This raises the possibility that exposure to air pollution may explain, in part, the differences in prognosis among heart attack patients from different backgrounds," said Dr. Tonne.
The researchers write in their conclusion “Despite higher exposure to PM2.5 among those from more deprived areas, such exposure was a minor contribution to the socioeconomic inequalities in prognosis following ACS. Our findings add to the evidence of mortality associated with long-term exposure to fine particles.”
In closing Dr. Tonne states "The implication is that while reducing levels of PM2.5 will lead to increased life-expectancy and is an important public health priority, it isn't likely to reduce socioeconomic inequalities in prognosis very much. There are likely to be many other factors that are more important than PM2.5 exposure in explaining socioeconomic inequalities in prognosis, and this requires further investigation."
Dr. Pier Mannucci, MD, Scientific Director of the IRCCS Ca' Granda Maggiore Policlinico Hospital Foundation in Milan, in an accompanying editorial writes; “The most important message is that reduction in the amount of pollutants in metropolitan areas does indeed decrease cardiovascular mortality within a time interval as short as a few years…”
He adds that the “huge toll of deaths…worldwide owing to air pollution could be substantially reduced – by approximately one million annually from the current estimate of 1.34 million – if the WHO [World Health Organization] recommendations pertaining to the limits of PM2.5 concentrations were implemented. The responsibility for controlling air pollution rests on national governments of the planet….”
He adds “in the meantime, individual clinicians should "make patients aware of the existence of this risk, and encourage them to be cognizant of the media alerts on air quality in their living areas." Finally, he calls on the European Society of Cardiology to develop scientific statements on air pollution and cardiovascular disease in order to make governments, clinicians and the public more aware of the problem.”
This study is published online in the European Heart Journal.
Tel Aviv University researchers concluded that not only does air pollution impact cardiac event such as heart attack and stroke, but it also cause repeated episodes over the long term.
The research was presented at the San Diego Epidemiological Meeting of the American Heart Association in March and the Annual Meeting of the Israeli Heart Society in April, 2012.