Abstract
As a non-invasive method, heart rate variability (HRV) has been widely used to study cardiovascular autonomous control. Environmental epidemiological studies indicated that the increase in an average concentration of particulate matter (PM) would result in a decrease in HRV, which was related to the increase of cardiovascular mortality in patients with myocardial infarction and the general population. With rapid economic and social development in Asia, how air pollutants, such as PM of different sizes and their components, affect the cardiovascular health of older people, still need to be further explored. The current study includes a 72 h personal exposure monitoring of seven healthy older people who lived in the Taipei metropolitan area. Mobile equipment, a portable electrocardiogram recorder, and the generalized additive mixed model (GAMM) were adopted to evaluate how HRV indices were affected by size-fractionated PM, particle-bound polycyclic aromatic hydrocarbons (p-PAHs), black carbon (BC), and carbon monoxide (CO). Other related confounding factors, such as age, sex, body mass index (BMI), temperature, relative humidity (RH), time, and monitoring week were controlled by fixed effects of the GAMM. Statistical analyses of multi-pollutant models showed that PM2.5–10, PM1, and nanoparticle (NP) could cause heart rate (HR), time-domain indices, and frequency-domain indices to rise; PM1–2.5 and BC would cause the frequency-domain index to rise; p-PAHs would cause HR to rise, and CO would cause time-domain index and frequency-domain index to decline. In addition, the moving average time all fell after one hour and might appear at 8 h in HRVs’ largest percentage change caused by each pollutant, results of which suggested that size-fractionated PM, p-PAHs, BC, and CO exposures have delayed effects on HRVs. In conclusion, the results of the study showed that the increase in personal pollutant exposure would affect cardiac autonomic control function of healthy older residents in metropolitan areas, and the susceptibility of cardiovascular effects was higher than that of healthy young people. Since the small sample size would limit the generalizability of this study, more studies with larger scale are warranted to better understand the HRV effects of simultaneous PM and other pollution exposures for subpopulation groups.
Highlights
Over the past decades, cardiovascular disease (CVD), cerebrovascular disease, and cancer have become the top causes of death in Taiwan, in the meantime, the rising trend of cardiovascular disease morbidity and mortality have gradually been the focus of public health policy and epidemiological research in Asian countries [1,2]
Personal exposures, including PM10, PM2.5–10, PM2.5, PM1–2.5, PM1, NP, particle-bound polycyclic aromatic hydrocarbons (p-polycyclic aromatic hydrocarbons (PAHs)), black carbon (BC), carbon monoxide (CO), temperature, and relative humidity (RH) were calculated in 5 min segments
This study found that the moving average concentrations of 1–3 h exposures to PM1 would cause a significant increase in the frequency-domain indicator high-frequency range (HF), while the moving average concentration of 4–8 h PM1–2.5 exposure would result in the rise of the heart rate variability (HRV) indicators low-frequency range (LF) and strongest association with the time-domain index (SDNN)
Summary
Cardiovascular disease (CVD), cerebrovascular disease, and cancer have become the top causes of death in Taiwan, in the meantime, the rising trend of cardiovascular disease morbidity and mortality have gradually been the focus of public health policy and epidemiological research in Asian countries [1,2]. Environmental cardiology has been an important field for public health practitioners and clinical researchers to explore the environmental risk factors of CVD and provide useful medical knowledge. HRV indices can be analyzed in the time-domain and frequency-domain and were proven as important indicators for cardiovascular disease morbidity and mortality. If SNS and PNS are unbalanced, it will affect the heart contraction that could lead to cardiovascular symptoms [5,6]
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