Nitrogen dioxide pollution reduces the benefits of cardiac rehabilitation after myocardial infarction by up to 90%

A study carried out by the Fundación Española del Corazón (FEC) and published in the journal Heliyon has revealed the significant impact of air pollution on recovery after myocardial infarction. The study, which involved seven hospitals from all over Spain and included a total of 137 patients, analysed how high levels of nitrogen dioxide (NO₂) in the environment reduce the benefits obtained from cardiac rehabilitation programmes.

“We included patients who had suffered an acute myocardial infarction between January 2015 and December 2019,” explained Dr Jordi Bañeras of the Cardiology Service of the Heart Knowledge Area of the Vall d'Hebron Hospital of Barcelona, researcher of the Cardiovascular Diseases Group of the Vall d'Hebron Research Institute (VHIR) and main author of the study. “Our hypothesis was that environmental pollution could limit the functional benefits of these programmes, which are essential for recovery after a heart attack.”

The patients included in the study were subjected to ergospirometry, an advanced stress test that measures physiological parameters such as maximum oxygen consumption, functional capacity and some indirect indicators of cardiovascular efficiency one month and three months after the heart attack.

The researchers focused on peak oxygen consumption (VO₂), a key indicator for measuring functional recovery after a heart attack. Of the different pollutants analysed, only nitrogen dioxide showed a significant correlation with reduced improvement in functional capacity.

“The results show, for the first time, that patients exposed to high levels of nitrogen dioxide in the two years prior to their heart attack exhibited reduced improvement in peak oxygen consumption after participating in a rehabilitation programme. Specifically, while those who lived in less polluted areas achieved an average improvement of 9.5% in their oxygen consumption, those who lived in highly polluted areas barely registered an increase of 0.9%” explained Dr Bañeras. This means that nitrogen dioxide pollution reduces the benefits of cardiac rehabilitation by up to 90%.

While pollution was already known to be a cardiovascular risk factor, the results of this study show that it also influences functional recovery after a heart attack. In light of this, Bañeras feels that cardiologists should advise patients to avoid polluted areas during follow-up.

In line with this evidence, hospitals such as Vall d'Hebron have already started to include warnings about environmental pollution in their hospital discharge plans after a heart attack, in addition to more common recommendations such as monitoring cholesterol and doing regular physical exercise.

The study, partially funded by the European Public Health Alliance (EPHA), involved the participation of the following hospitals, in addition to Vall d'Hebron: Hospital Universitario de Toledo, Hospital de Mataró, Hospital Universitario de Donostia, Hospital Universitario Virgen del Rocío, Hospital Universitario 12 de Octubre, Hospital General Universitario Santa Lucía and the Clínica Colman.