The association of ambient air pollution and abnormal left ventricular diastolic function

A recent study published in BMC Public Health investigated the associations between abnormal left ventricular diastolic function (ALVDF) and ambient air pollution.

Study: Air pollution is associated with abnormal left ventricular diastolic function: a nationwide population-based study. Image Credit: Toa55/Shutterstock.com

Background

Air pollution has been a significant concern for global public health, with >90% of the world's population exposed to particulate matter 2.5 (PM_2.5) levels higher than the air quality guidelines of the World Health Organization (WHO).

Evidence suggests that the burden of air pollution-related cardiovascular disease (CVD) is greater than previous estimates. Left ventricular diastolic dysfunction is an early cardiac dysfunction sign that predicts non-fatal and fatal cardiovascular events.

Moderate or mild diastolic dysfunction has been linked to an increased mortality risk in asymptomatic individuals. Although the association of air pollution with CVD morbidity and mortality is well documented, there is limited evidence of the relationship between cardiac imaging phenotypes and air pollutants.

Previously, the study's authors reported that the relationship between CVD and diastolic dysfunction worsened with ambient air pollution. Regardless, the impact of air pollution on left ventricular function in large populations is unclear.

About the study

In the present study, researchers investigated the associations between exposure to ambient air pollutants and ALVDF. They obtained data from an extensive cross-sectional survey conducted in China, which included individuals aged 35 or older from 14 provinces. Ventricular function was evaluated using echocardiography.

Diastolic dysfunction was categorized into grades I (impaired relaxation pattern), II (pseudo-normal), and III (severe). The average annual concentrations of nitrogen dioxide (NO₂), PM_2.5, and PM₁₀, were obtained from an air quality dataset for 2013-18. The effect of average annual air pollutant levels was investigated.

Standardized questionnaires were administered to capture data on demographics, lifestyle behaviors, medical history, and family CVD history. Participants were instructed to provide information on indoor ventilation or air pollution, solid fuel usage, and exposure to passive smoke.

The altitudes of surveyed sites were estimated, and participants' blood pressure and body weight were measured. Blood specimens were collected after eight hours of overnight fasting.

Group differences were compared using the chi-squared test. Multivariate logistic regression calculated odds ratios for the association between air pollution and diastolic function.

Models were adjusted for sex, age, urbanicity, ethnicity, habitation altitude, smoking or drinking status, obesity, family CVD history, education, hyperlipidemia, hypertension, diabetes, solid fuel use, and second-hand smoke exposure.

Findings

The researchers identified more than 30,000 participants; of these, 630 and 3,423 individuals were excluded due to prior CVD history and missing echocardiography data, respectively. In total, 25,983 individuals were included for analysis. Subjects were aged, on average, 56.8, and 46.5% were males, and the crude ALVDF prevalence was 50.8%.

The average annual concentrations of NO₂, PM_2.5, and PM₁₀ were 29.87 μg/m³, 62.77 μg/m³, and 94.22 μg/m³, respectively. Approximately one-fourth of the cohort used solid fuels, and 8.5% were exposed to second-hand smoke.

Males had higher fasting blood glucose, blood pressure, triglycerides, and ALVDF prevalence but were less exposed to indoor air pollution and ambient PM_2.5.

Increased exposure to air pollutants was significantly associated with elevated risks of ALVDF. The odds ratios for the risk of grade I ALVDF per 10 μg/m³ increment of NO₂, PM_2.5, and PM₁₀ were 1.28, 1.42, and 1.15, respectively. No significant association was observed between air pollutant levels and grade II or III ALVDF risk.

Odds ratios for the grade II or III ALVDF risk per 10 μg/m³ increment of air pollutant levels ranged from 0.22 to 0.97.

The researchers observed a positive linear, non-linear, and J-shaped concentration-response association of the average annual PM_2.5, PM₁₀, and NO₂ levels with the risk of ALVDF, respectively.

Conclusions

The study was the first to examine associations between air pollution and ALVDF risk in a large (asymptomatic) population. The findings revealed a significant association between ambient air pollutant levels and ALVDF risk.

Specifically, increased concentrations of air pollutants were significantly associated with grade I ALVDF but not grade II or III ALVDF.

The researchers speculate that the impact of air pollutants on cardiac function was limited. Appropriate interventions for reducing air pollution may offer potential public health benefits.

Written by

Tarun Sai Lomte

Tarun is a writer based in Hyderabad, India. He has a Master’s degree in Biotechnology from the University of Hyderabad and is enthusiastic about scientific research. He enjoys reading research papers and literature reviews and is passionate about writing.