Health measures introduced during the COVID-19 pandemic – particularly mask-wearing – may have helped protect people from a specific type of heart attack linked to air pollution, new research suggests.
Drawing on data from Japan’s nationwide cardiovascular registry, researchers analysed 270,091 heart attack hospitalisations from 2012 to 2022. They compared the effects of short-term air pollution exposure before and during the pandemic, when widespread mask-wearing and reduced mobility fundamentally altered how people interacted with polluted air.
It was found that short-term exposure to PM2.5 increases the risk of heart attack. For every 10 μg/m³ rise in PM2.5 levels two days before admission, the odds of a heart attack increased by around 10%.
But the study uncovered a more striking pattern when it looked at a specific subtype: MINOCA (myocardial infarction with non-obstructive coronary arteries). Unlike typical heart attacks, where arteries are blocked by plaques, MINOCA is often caused by temporary artery spasm or microvascular dysfunction – mechanisms particularly sensitive to inflammation and oxidative stress.
Before the pandemic, a 10-unit increase in PM2.5 was associated with a 30% higher risk of MINOCA. After April 2020, when Japan declared a state of emergency and mask-wearing became near-universal, this association weakened and was no longer statistically significant.
The authors write: ‘This observed reduction in MINOCA risk following the COVID-19 pandemic suggested that public health interventions aimed at reducing air pollution exposure may reduce cardiovascular risks, particularly in specific AMI subtypes.’
The same pattern was not seen for typical obstructive heart attacks, where the pollution-related risk remained largely unchanged. The researchers suggest this may reflect the different biological pathways involved.
MINOCA is thought to arise from dysfunction in the lining of blood vessels (the endothelium) and the smooth muscle of artery walls. Both can be aggravated by oxidative stress triggered by PM2.5. By filtering out pollution particles, masks may have dampened this inflammatory process.
The study’s lead author, Dr Masanobu Ishii of Kumamoto University, noted that while Japan’s ambient PM2.5 levels did not fall dramatically during the pandemic, behavioural changes – especially widespread mask use – may have been the critical factor.
The researchers point out that while the reduction in risk for any given person was small, when applied across an entire population, it can add up to preventing thousands of heart attacks.
They add that the findings also highlight a potentially preventable pathway for MINOCA – a condition with historically few targeted treatment options.
As one researcher put it, the pandemic provided a ‘natural experiment’ and the results suggest that simple measures like wearing masks could have lasting benefits beyond infectious disease control.
The full research can be read here
Photo: Pexels
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