Air pollution affects human health. A new study, published on September 28 in the American magazine Neurology by Fei Tian, from Sun-Yat-sen University in Canton (China), and his colleagues confirms that exposure to polluted air, in particular to fine PM2.5 particles – with a diameter of less than 2.5 micrometers (µm ) –, increases the risk of suffering a cerebrovascular accident (CVA). But it also reveals, in an unprecedented way, that breathing an atmosphere polluted, in particular by nitrogen dioxide (NO2), increases the risk for people who have had a stroke of later developing cardiovascular disease.
The researchers worked on a large number of people: nearly 320,000 people aged 40 to 69 enrolled in the UK Biobank. This large UK cohort, with easily accessible data, is ideal for “allow researchers to identify risk factors for many complex diseases occurring in middle and old age”underlines one of the co-authors of the study, Hualiang Lin.
Nearly 6,000 study participants
The researchers therefore looked at the evolution, over an average of twelve years, of the participants in the cohort without a history of stroke, heart disease linked to vascular problems or cancer, and for whom data on exposure to atmospheric pollutants were available. A total of 5,967 suffered a stroke, of which about half (2,985) subsequently developed cardiovascular disease (heart failure, myocardial infarction, arrhythmia or coronary artery disease). Of these, 1,020 died during the follow-up period.
What is the role of air pollution in relation to these pathologies and deaths? To find out, the researchers estimated the annual concentration of fine particles (PM2.5 and PM10), in NO2 or in nitrogen oxides (NOx) near the place of residence of the participants at the start of the follow-up.
On this basis, and after taking into account a series of confounding factors – including smoking, alcohol consumption, body mass index (BMI) and physical activity – the researchers calculated that the risk of stroke occurrence increased by 24% for each 5 μg increase in PM2.5 per cubic meter of air. A more modest but significant effect was also observed for NO2with a 2% increased risk of stroke for each increase of 5 μg/m3.
The risk of dying without having had a stroke was also increased, on the order of 30% for each increase of 5 μg/m3 of PM2.5, and 3% for each increase of 5 μg/m3 not2.
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