A research team led by the Barcelona Institute for Global Health (ISGlobal), an organization aided by “la Caixa,” has, for the first time, investigated the connection between ambient and household air pollution and carotid intima-media thickness (CIMT), a marker of atherosclerosis, in a population of a low-and-middle-income country.
The study, carried out in a periurban area in southern India, reveals that people most exposed to fine particles have a greater CIMT index, implying that they are at a greater risk of developing cardiovascular diseases such as heart attack or stroke.
Earlier studies point out that atherosclerosis and inflammation are almost certainly responsible for the connection between prolonged exposure to air pollution and cardiovascular disease and death.
Atherosclerosis is marked by an accumulation of cholesterol, fat, and other substances along the artery walls. A non-invasive method to detect atherosclerosis is to determine the thickness of the innermost layers of the carotid artery (CIMT) using ultrasound.
Until now, studies connecting CIMT with exposure to air pollution were restricted to high-income nations or to average levels of air pollution.
Now, the team working for the CHAI project has published a new research that investigates such a link in India, a lower middle-income nation with high air pollution levels. The research, published in the International Journal of Epidemiology, surveyed 3,372 participants from a periurban region of Hyderabad, Telangana, in southern India.
The researchers used an algorithm known as land use regression (LUR) to measure CIMT and estimate the exposure to air pollution. The LUR algorithm is generally used to estimate the amount of fine particles (suspended particles with a diameter of <2.5 μm) in high-income nations. The participants also offered information on the kind of fuel they used for cooking.
The results show that high yearly exposure to ambient fine particles was related to a higher CIMT, specifically in men, participants over the age of 40, or those with cardiometabolic risk factors.
It was revealed that 60% of the participants used biomass cooking fuel.
People using biomass fuel for cooking had a higher CIMT, particularly women who cooked in unventilated spaces. Women had a higher CIMT than men, which could be due to the fact that they spend more time in the kitchen, breathing air polluted by biomass fuel.
Otavio Ranzani, Study First Author and Researcher, ISGlobal
Yearly average exposure to PM2.5 was 32.7 μg/m3 much above the WHO-recommended levels of 10 μg/m3.
This study is relevant for countries which, like India, are experiencing a rapid epidemiological transition and a sharp increase in the prevalence of hypertension, diabetes, and obesity. In addition, the country is affected by high levels of air pollution, both ambient and indoors.
Cathryn Tonne, Study Coordinator and Researcher, ISGlobal
Tonne added, “Our findings highlight the need to perform more studies on air pollution in low- and middle-income countries, since the conclusions may differ considerably from studies in high income countries due to differences in population characteristics and air pollution levels and sources.”
Tonne is also the coordinator of the CHAI project.