Obstructive sleep apnoea (OSA) symptoms may worsen for patients who live in areas with higher levels of air pollution, a multi-national study has found.
Involving patients with OSA in 25 different cities across 14 countries, the study was exclusively presented at the European Respiratory Society Congress.
As well as causing excessive sleepiness, OSA can increase the risk of high blood pressure, stroke, heart disease and type 2 diabetes.
‘We know that OSA is more common in people who are older or overweight, but there’s growing concern that air pollution also might make the condition worse,’ explained Martino Pengo, associate professor at the University of Milano-Bicocca and consultant physician and senior researcher in the Department of Cardiovascular, Neural and Metabolic Sciences at the IRCCS Italian Auxological Institute in Milan, Italy.
‘However, previous studies, mostly focused on just one country, have produced mixed results. We wanted to look at this on a larger scale, across several European cities, to better understand if and how air pollution affects OSA.’
Modest but measurable increase in patient AHI
Data from 19,325 patients with obstructive sleep apnoea from 25 different cities in 14 countries were analysed as part of the study. All patients were taking part in a larger research project – the European Sleep Apnoea database.
In addition to providing data on their age, sex, body mass index and whether they smoked, all patients took part in a sleep study to measure their sleep quality and confirm a diagnosis of OSA. This included recording pauses in breathing and drops in the level of oxygen in the blood.
The researchers combined this patient data with records of particulate matter 10 (PM10) concentration in the air where each patient lived. This is the amount of inhalable particles measuring 10 micrometres or less, which are released into the air by vehicle exhausts, industrial processes and other sources of pollution.
PM10 concentration data was taken from the Europe-wide Copernicus Atmosphere Monitoring Service.
Overall, for every one unit increase in PM10, there was a modest but measurable increase in the patients’ apnoea hypopnea index (AHI), which is the number of apnoeas and hypopneas per hour during sleep.
For patients with low AHI of less than five, the average PM10 in the area where they live was relatively low at around 16 micrograms per cubic metre of air. In contrast, patients with high AHI of five or more, the average PM10 was also higher at around 19 micrograms per cubic metre of air.
Significant positive association between air pollution and OSA
‘We confirmed a statistically significant positive association between average long-term exposure to air pollution, specifically fine particles known as PM10, and the severity of OSA,’ explained Professor Pengo.
‘Even after we took account for other factors that we know have an effect on OSA, we still found an average increase in the number of respiratory events per hour of sleep of 0.41 for every unit increase in PM10. This effect may seem small for an individual, but across entire populations it can shift many people into higher-severity categories, making it meaningful from a public health perspective.’
The analysis also identified differences between the strength of the link between air pollution and OSA in different cities across Europe. For example, in cities such as Lisbon, Paris and Athens, the association was particularly strong.
‘In some cities, the impact was stronger,’ Professor Pengo added. ‘In others, it was weaker or even absent. These regional differences might be due to things like local climate, the type of pollution or even how healthcare systems detect OSA.’
Following on from this study, the researchers want to understand specifically why the effects vary between cities, and whether some people are more affected by air pollution than others. Exploring whether reducing air pollution can improve OSA symptoms is also a priority.
Professor Sophia Schiza, head of the European Respiratory Society’s expert group on sleep disordered breathing, commented: ‘For doctors caring for people with OSA, this research highlights the need to consider environmental factors like air quality alongside other risk factors. This study strengthens the connection between environmental health and sleep medicine. It reminds us that tackling air pollution isn’t just good for the planet, it’s also vital for our lungs and our sleep quality too.’