New Study Links Air Pollution to HF Hospitalization and Mortality

Air pollution has a close temporal association with heart failure hospitalization and heart failure mortality, according to a systematic review and meta-analysis of data from 12 countries published in The Lancet.

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The analysis focused on studies published between 1948 and July 15, 2012 assessing the impact of daily increases in gaseous air pollutants (carbon monoxide, sulphur dioxide, nitrogen dioxide, and ozone) and particulate matter (PM) with a diameter of 2.5 micrometers (PM2.5) or less, or 10 micrometers (PM10) or less, on the risk of hospitalizations or death due to heart failure. Of the 1,146 articles identified, 195 were reviewed in-depth with 35 satisfying inclusion criteria.

Overall, data showed a positive association between heart failure hospitalization or heart failure mortality, and all gaseous and particulate air pollutants except ozone. According to the authors, carbon monoxide was the most frequently studied gaseous pollutant, and showed a 3.52% (95% CI 2.52–4.54%) increase in heart failure hospitalizations or mortality per 1 part per million increment across nearly two million events. Sulphur dioxide and nitrogen dioxide were associated with increased risks of 2.36% per 10 parts per billion and 1.70% per 10 parts per billion, respectively. In terms of particulate matter, hospitalizations and death increased 2% for every increase of 10 micrograms per cubic meter of particulate matter, with strongest associations occurring on the day of exposure. In addition, median daily PM2.5 concentrations varied across states, "with the highest population-attributable risks seen in Mississippi, Kentucky, and Tennessee and the lowest in Utah, Wyoming, and North Dakota."

Given the study results, the authors suggest that an estimated mean reduction in PM2.5 of 3 · 0 µg/m^3 would prevent 7,978 heart failure-related hospitalizations and save $307 million annually in the U.S. alone. They also note that in additional analysis stratifying studies by location risk estimates were almost twice as high in countries outside the U.S. where ambient concentrations are generally higher. "As such, caution is necessary when extrapolating overall risk estimates from our meta-analysis to regions with higher air pollution concentrations," they said.

Moving forward, the authors stress the need for further studies to test the relationship between air pollution and heart failure, as well as highlight opportunities for global intervention. "Although the causality and biological mechanisms need further exploration, air pollution is a pervasive public health issue with major cardiovascular and healthcare economic consequences presenting a key target for national and international intervention," they said.

Commenting on the study Francesco Forastiere and Nera Agabiti from Lazio Regional Health Service in Rome, Italy, say, "This report is…timely, since 2013 has been declared the Year of Air by the European Union (EU). The current EU limit for fine particulate matter is 25 μg/m³ (annual average, which is higher than the 10 μg/m³ set by WHO); however, the adverse health effects of air pollution are present even at concentrations well below this limit. The European Respiratory Society's Ten Principles for Clean Air state that "citizens are entitled to clean air, just like clean water and safe food." In light of Shah and colleagues' report, these principles should be pursued by all necessary means, especially within the context of EU legislation."

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