Air pollution strongly correlated with atherogenesis; intervention study planned

A study by the Chinese University of Hong Kong (CUHK) and Chongqing Medical University finds a strong association between air pollution and markers of early atherosclerosis, suggesting a potential target for preventive intervention.

“Particulate matter with an aerodynamic diameter <2.5 µm [PM2.5] can trigger low-grade pulmonary inflammation and thus lead to systemic vascular inflammation–induced atherosclerosis,” said Professor Timothy Kwok of the Department of Medicine and Therapeutics at CUHK.

Air pollution has been associated with an increase in cardiovascular disease (CVD) incidence. [Arch Cardiovasc Dis 2017;110:634-642] To evaluate whether air pollution can accelerate atherogenic processes, the researchers assessed the effects of air pollution on two surrogate markers of atherosclerosis, namely, brachial flow-mediated dilation (FMD) and carotid intima-media thickness (CIMT). [Int J Epidemiol 2021;50:578-588]

“Changes in the incidence and mortality of CVD and stroke usually appear 10–20 years following intervention. On the other hand, changes in the prognostic surrogates, including CIMT and FMD, after intervention can be witnessed in just a few months, suggesting a promising approach for evaluating PM2.5-related atherosclerosis prevention programmes,” explained Kwok.

The researchers evaluated data from 1,656 Han Chinese subjects (mean age, 46.0 ± 11.2 years; male, 47 percent) residing in Hong Kong, Macau, Pun Yu, Yu County and the Three-Gorges Territories (Yangtze River) between 1996 and 2007 enrolled in the CATHAY (Chinese Atherosclerosis in The Aged and Young Project) study. Health parameters, namely, gender, body mass index, waist-to-hip ratio (WHR), and glucose, were used to assess cardiovascular risk. PM2.5 data were computed from satellite sensors, and brachial FMD and CIMT were measured by ultrasound.

The health parameters were similar between lowest and highest PM2.5 exposure tertiles, while systolic and diastolic blood pressures (BPs) and triglycerides were higher (p<0.001) and LDL-cholesterol (LDL-C) was lower in the top PM2.5 tertile (p<0.001). Median brachial FMD was significantly lower (7.84 percent vs 8.50 percent; p<0.0001) and median CIMT was significantly thicker (0.68 mm vs 0.63 mm; p<0.0001) in the top vs lowest PM2.5 tertile vs the lowest tertile.

“According to a study conducted in the Netherlands, the observed 8 percent CIMT difference is equivalent to a 41 percent increase in stroke and 43 percent increase in heart attack over a follow-up period of 2–7 years, and comparable with the difference seen between diabetic and nondiabetic adults, with significant long-term health implications,” commented the researchers. [Circulation 1997;96:1432-1437]

Multiple regression analysis showed that FMD was inversely related to PM2.5 (β, 0.134; p=0.015) independent of gender, age and BP (model R2, 0.156; F-value, 7.6; p<0.0001). At the same time, CIMT was significantly correlated with PM2.5 exposure (β, 0.381; p<0.0001) independent of age, location, gender, WHR, BP and LDL-C (model R2, 0.408; F-value, 51.4; p<0.0001).

To overcome challenges caused by air pollution and CVD, the researchers will be launching a study, where subjects (including workers in highly polluted environments, such as bus/taxi drivers, cooks and builders) will be randomized to receive a pulmonary anti-inflammatory agent, montelukast, or placebo for 6 months, followed by comparison of their FMD and CIMT.

“This interventional study will further prove the correlation between air pollution and CVD and provide a strong foundation for future interventions to prevent the disease,” said lead author, Dr Kam Woo, of the Department of Medicine at CUHK.