Exposures to low-levels of fine particulate matter are associated with acute changes in heart rate variability, cardiac repolarization, and circulating blood lipids in coronary artery disease patients

Abstract

Exposure to air pollution is a major risk factor for cardiovascular disease, disease risk factors, and mortality. Specifically, particulate matter (PM), and to some extent ozone, are contributors to these effects. In addition, exposures to these pollutants may be especially dangerous for susceptible populations. In this repeated-visit panel study, cardiovascular markers were collected from thirteen male participants with stable coronary artery disease. For 0-4 days prior to the health measurement collections, daily concentrations of fine PM (PM_2.5) and ozone were obtained from local central monitoring stations located near the participant's homes. Then, single (PM_2.5) and two-pollutant (PM_2.5 and ozone) models were used to assess whether there were short-term changes in cardiovascular health markers. Per interquartile range increase in PM_2.5, there were decrements in several heart rate variability metrics, including the standard deviation of the normal-to-normal intervals (lag 3, -5.8%, 95% confidence interval (CI) = -11.5, 0.3) and root-mean squared of successive differences (five day moving average, -8.1%, 95% CI = -15.0, -0.7). In addition, increases in PM_2.5 were also associated with changes in P complexity (lag 1, 4.4%, 95% CI = 0.5, 8.5), QRS complexity (lag 1, 4.9%, 95% CI = 1.4, 8.5), total cholesterol (five day moving average, -2.1%, 95% CI = -4.1, -0.1), and high-density lipoprotein cholesterol (lag 2, -1.6%, 95% CI = -3.1, -0.1). Comparisons to our previously published work on ozone were conducted. We found that ozone affected inflammation and endothelial function, whereas PM_2.5 influenced heart rate variability, repolarization, and lipids. All the health changes from these two studies were found at concentrations below the United States Environmental Protection Agency's National Ambient Air Quality Standards. Our results imply clear differences in the cardiovascular outcomes observed with exposure to the two ubiquitous air pollutants PM_2.5 and ozone; this observation suggests different mechanisms of toxicity for these exposures.

Keywords: Air pollution; Cardiovascular; Coronary artery disease; Heart rate variability; Lipids; Particulate matter.

Fig. 1.. Mean daily PM_2.5 concentrations (μg/m³) between May 30, 2012-April 29, 2014.

Daily 24-hr PM_2.5 (μg/m³) concentrations (9 a.m.–8 a.m.) were calculated from the Millbrook central monitor.

Fig. 2.. Percent changes from Holter monitoring with ambient PM_2.5 concentrations.

(A) Percent changes of SDNN and rMSSD, (B) Percent changes with HF and LF, (C) Percent changes with P and QRS complexity. Effect estimates (95% CI) were log-transformed, correspond to changes per IQR of PM_2.5, and were adjusted for season, temperature, and humidity. IQR = interquartile range; 5dMA = 5 day moving average; SDNN = standard deviation of the normal-to-normal; rMSSD = root-mean squared of successive differences; HF = high frequency; LF = low frequency.

Fig. 3.. Percent changes of inflammation markers with ambient PM_2.5 concentrations.

Effect estimates (95% CI) were log-transformed, correspond to changes per IQR of PM_2.5, and were adjusted for season, temperature, and humidity. IQR = interquartile range; 5dMA = 5 day moving average; TNF = tumor necrosis factor.

Fig. 4.. Percent changes of cholesterol with ambient PM_2.5 concentrations.

Effect estimates (95% CI) were log-transformed, correspond to changes per IQR of PM_2.5, and were adjusted for season, temperature, and humidity. IQR = interquartile range; 5dMA = 5 day moving average; HDL-C = high-density lipoprotein cholesterol.

Fig. 5.. Percent changes of clotting and fibrinolysis factors with ambient PM_2.5 concentrations.

Effect estimates (95% CI) were log-transformed, correspond to changes per IQR of PM_2.5, and were adjusted for season, temperature, and humidity. IQR = interquartile range; 5dMA = 5 day moving average; tPA = tissue plasminogen factor.