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Pollution increases heart attack risk

"Controversial" research linking pollution levels with heart attacks has been criticised as being "ambiguous" and "unclear" by the British Heart Foundation.

The study, published in the British Medical Journal, found that high levels of pollution increases the risk of having a heart attack for up to six hours after exposure.

However, no increased risk was found after the six-hour time frame.

This led Krishnan Bhaskaran, an epidemiologist from the London School of Hygiene and Tropical Medicine, and his team to suggest high pollution levels "merely brought the heart attack forward by a couple of hours."

Jeremy Pearson, an associate medical director at the British Heart Foundation, told Nursing in Practice such interpretations of the research would be damaging to its campaign to reduce pollution levels.

Pearson also believes the study's conclusion that such heart attacks were "inevitable" to be incorrect.

He claims the people studied may have not had heart attacks "for another ten years" had they not be exposed to such high levels of pollution.

The authors also argue there may be "limited potential for reducing the overall burden of heart attacks through reductions in pollution alone".

Pearson told NiP, there was "absolutely no evidence to support this statement".

"This is controversial research," said Pearson.

"While the data is sound, the wording allows the research to be open to interpretation, which is damaging."

Pearson also said two other researchers have logged complaints with the BMJ claiming the wording of the study to be "unclear".

Bhaskaran acknowledges the research will not provide a major health concern for the public, as it will not be viewed as "significant enough".

However, he defends the study's conclusions and claims they cannot be misinterpreted, believing Pearson to be mixing up pollution level links with other heart-related problems.

The study's methodology has also been called into question.

Researchers reviewed 79,288 heart attack cases from 2003 to 2006 and exposure, by the hour, to pollution levels.

Professor Richard Edwards and Dr Simon Hales from the University of Otago in New Zealand claim "it is possible that a true effect was missed because of imprecise measurements and inadequate statistical power."

Hales said that other studies suggest exposure to high levels of pollution from daily or longer timescales does have an important effect on a heart attack risks.

Bhaskaran agrees with the criticism and told NiP there were limitations of the study.

"It is always a trade off," he said.

"We chose research on a large scale to give us 'study power', but that does mean we missed individual circumstances."

British Heart Foundation