Air pollution affects human health. A new study, published on September 28 in an American magazine neurology Fei Tian, from Sun-Yat-sen University in Guangzhou (China) and his colleagues confirm that exposure to polluted air, especially PM2.5 fine particles – less than 2.5 micrometers (µm) in diameter – increases the risk of cerebrovascular accident (CMP). But it also reveals in an unprecedented way that breathing an atmosphere polluted, especially by nitrogen dioxide (NO2), increases the risk of later developing cardiovascular disease in people who have had a stroke.
The researchers worked on a large number of people: almost 320,000 people aged 40 to 69 registered in the British Biobank. This large UK cohort with readily available data is ideal for “Enable researchers to identify risk factors for many complex diseases occurring in middle age and old age”points out one of the co-authors of the study, Hualiang Lin.
Nearly 6,000 study participants
The researchers therefore looked at the development, over an average of twelve years, of participants in a cohort without a history of stroke, heart disease associated with vascular problems or cancer, and for whom data on exposure to atmospheric pollutants were available. A total of 5,967 had 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 where the participants lived at the start of follow-up.
On this basis, and after taking into account a range of confounding factors – including smoking, alcohol consumption, body mass index (BMI) and physical activity – the researchers calculated that the risk of stroke increased by 24% for every 5 μg increase in PM2.5 per cubic meter of air . A smaller but more significant effect was also observed for NO2with a 2% increased risk of stroke for every 5 μg/m increase3.
The risk of non-stroke death also increased, on the order of 30% for each 5 μg/m increase3 PM2.5 and 3% for each 5 μg/m increase3 from NO2.
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