Air Pollutants Up Heart-Failure Deaths, Hospitalizations, Costs

Shelley Wood

July 09, 2013

LONDON, UK — Modest reductions in air pollution could prevent almost 8000 hospitalizations for heart failure and save hundreds of millions of healthcare dollars in the US alone, authors of a new study estimate[1].

Dr Anoop SV Shah and colleagues (University of Edinburgh, Scotland) combined data from 35 studies addressing the health effects of air pollution that included heart-failure end points. In all, data from 12 countries were included in their review, published online today in the Lancet.

They found that of the common airborne pollutants, carbon monoxide was the most frequently studied and was associated with the largest increase in heart-failure hospitalizations or death, although all "gaseous and particulate air pollutants" (with the exception of ozone) were associated with increased HF hospitalization or HF mortality.

HF hospitalization or mortality was increased by 3.52% for every 1-ppm increase in carbon monoxide. For sulfur dioxide and nitrogen dioxide, the corresponding increase in risk was 2.36% and 1.70%, respectively, for every 10-ppb increase. For every 10-µg/m3-increase in particulate matter, HF hospitalizations or mortality was increased by 2%.

Of note, hospitalizations and deaths from HF peaked at times when air quality was the worst, Shaw and colleagues observed.

Saving Lives and Money

Responding to questions from heartwire , study coauthor Dr David McAllister (University of Edinburgh) stressed that he and his colleagues are not advising patients or clinicians to alter treatments or behavior as a result of the findings.

"The risk to an individual is small, but we are all exposed to air pollution and the effect on the population is important," he said in an email. "Clinicians can have a powerful voice on behalf of their patients advocating for public policies that reduce air pollution, thereby preventing admission to the hospital and early death for some patients with heart failure."

"There have been no previous systematic reviews of the effects of air pollution on heart-failure hospitalization," McAllister noted, and "relatively few studies in patients with heart failure. This is perhaps surprising given the prevalence of heart failure has been inexorably rising due to an aging population and the improved treatment of myocardial infarction. In the United States, the prevalence of heart failure is currently 2% and is expected to rise by 25% by 2013, and there were 4.2 million emergency-department attendances in 2010 for chronic heart failure, with total healthcare costs of $32 billion."

"All studies except one were done in developed countries where even modest improvements in air-quality standards are projected to have major population health benefits and substantial healthcare cost savings," Shah et al write. By their estimate, a reduction in small-particle (<2.5 µm) pollutants of just 3.9 µg/m3 would "save a third of a billion US dollars a year" and prevent 7973 HF hospitalizations.

"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."

Setting Limits, Understanding Impact

In an accompanying editorial[2], Drs Francesco Forastiere and Nera Agabiti (Lazio Regional Health Service, Rome, Italy) point out that the European Union designated 2013 the "Year of Air," yet the current limit, averaged annually, for fine particulate matter is 25 µg/m3. This, they note, is substantially higher than the target set by the WHO at 10 µg/m3, and clearly "adverse health effects of air pollution are present even at concentrations well below this limit."

In the cities Shah et al's analysis, the median concentration of particulate matter <2.5 µg was 15 µg/m3, but the authors note that daily fine-particulate-matter concentrations in cities with over 10 million people (eg, New Delhi and Beijing) are estimated at 100 to 300 µg/m3.

Previous studies of air pollution and cardiovascular events have focused primarily on myocardial infarction and atherosclerosis.

A second paper appearing in the Lancet today shows that even very low levels of air pollution increase the risk of lung cancer[3]. In that analysis, Dr Ole Raaschou-Nielsen (Danish Cancer Society Research Center, Copenhagen) and colleagues show that the risk of lung cancer rose by 18% with every 5-µg/m3 increase in pollution by particulate matter <2.5 µg and even higher with larger-particulate pollution.

Although the increases associated with heart-failure deaths and hospitalizations "are somewhat smaller than for lung cancer, heart failure is considerably commoner than lung cancer, and so the impact on heart failure across the population is nonetheless very important," McAllister pointed out. "In other words, while the effect on individuals may be small, for populations as a whole the effect of air pollution is considerable."

The authors for both papers and accompanying editorial declared having no conflicts of interest.

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