Effects of Different Size Particulate Matters on Heart Rate Variability in the Elderly People

Abstract

P-399 Introduction: Environmental epidemiologic studies have shown that the elderly people are susceptible for particulate air pollution. The decreases in heart rate variability (HRV) are important indices of health effect caused by particulate matter (PM). The objective of this study was to investigate the short-term effects of submicron particle (PM1), PM1–2.5, and coarse particle (PM2.5–10) on HRV parameters in the elderly. Method: The study population consisted of 15 non-smoking volunteers aged from 53 to 75 yrs, all of whom resided in the metropolitan Taipei area, Taiwan. Personal PM exposures were measured using a direct-reading portable dust monitor (GRIMM Model 1.108, Germany) in 1-minute interval, while each subject’s 24-hour electrocardiographics were recorded by a PacerCorder® holter recorder (DELMAR™ Medical LLC., model 461A, USA) in 5-minute interval. For each subject, health status and environmental factors were assessed by questionnaire and activity diary. The mass concentrations of PM1, PM1–2.5, and PM2.5–10 were measured and recorded as 1-hour, 2-hour, 3-hour, 4-hour, 5-hour, 6-hour, 7-hour, and 8-hour moving averages. Linear mixed-effects models were applied to estimate the effects of PM on time domain indices and frequency domain indices of HRV, using interquartile range (IQR) increase in PM concentrations. Time domain HRV parameters included the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD). Frequency domain HRV parameters included low frequency (LF) and high frequency (HF). Results: After adjusting for gender, age, body mass index, sleeping hours, β-block medicine, disease type, temperature, and relative humidity, the 3-hour moving averages of PM1 concentrations were found to have the strongest impact on HRV parameters. The strongest effects of PM1–2.5 on the decreases in SDNN, LF, and HF were shown for the 3-hour moving average, while the effect on r-MSSD decrease was the strongest for the 4-hour moving average. The largest decreases in SDNN, LF, r-MSSD, and HF for the effects of PM2.5–10 were found for 8 hours, 8 hours, 7 hours, and 4 hours moving averages, respectively. In addition, the impact of 3-hour PM moving average on the HRV decrease displayed the order of PM2.5–10 > PM1 > PM1–2.5, while only PM2.5–10 showed a significant impact on the HRV decrease after 5 hours. Conclusions: Results of our study indicated that PM may have both of the short-term effects and the delayed effects on HRV reduction in the elderly, with stronger delayed effect found for coarse particles in comparison with particles of other size ranges. Compared to the IQR concentrations of PM1 and PM1–2.5, coarse particles demonstrated a larger impact on the decrease in HRV for the elderly people.