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DAILY VARIATION OF PARTICULATE AIR POLLUTION AND POOR CARDIAC AUTONOMIC CONTROL IN THE ELDERLY
Citation:
Liao, D., J P. Creason, C. Shy, R Williams, R R. Watts, AND R Zweidinger. DAILY VARIATION OF PARTICULATE AIR POLLUTION AND POOR CARDIAC AUTONOMIC CONTROL IN THE ELDERLY. ENVIRONMENTAL HEALTH PERSPECTIVES 107(7):521-525, (1999).
Description:
Particulate matter air pollution (PM) has been related to cardiovascular disease mortality in a number of recent studies. The pathophysiologic mechanisms for this association are under study. Low heart rate variability, a marker of poor cardiac autonomic control, is associated with higher risk of myocardial infarction and sudden cardiac death. To address the possible mechanisms for PM-cardiovascular disease mortality, we examined the cardiac autonomic response to daily variations in PM in 26 elderly (mean age 81) individuals for 3 consecutive weeks. Several standardized methods were used to measure 24-hr average PM concentrations prior to the clinical test inside (indoor PM2.5) and immediately outside (outdoor PM2.5 and PM2.5-10) of participants' residences. Resting, supine, 6-min R wave to R wave (R-R) interval data were collected to estimate high frequency (0.15-0.40 Hz) and low frequency (0.04-0.15 Hz) powers and standard deviation of normal R-R intervals (SDNN) as cardiac autonomic control indices. Participant-specific lower heart rate variability days were defined as days for which the high-frequency indices fell below the first tertile of the individual's high-frequency distribution over the study period. Indoor PM2.5 > 15 ?g/m3 was used to define high pollution days. Results show that the odds ratio (95% confidence interval) of low heart rate variability high frequency for high (vs. not high) pollution days was 3.08 (1.43, 6.59). The ?-coefficients (standard error) from mixed models to assess the quantitative relationship between variations in indoor PM2.5 and the log-transformed high frequency, low frequency, and SDNN were: -0.029 (0.010), -0.027 (0.009), and -0.004 (0.003), respectively. This first study of cardiac autonomic control response to daily variations of PM2.5 indicates that increased levels of PM2.5 are associated with lower cardiac autonomic control, suggesting a possible mechanistic link between PM and cardiovascular disease mortality.
