Daily variation of particulate air pollution and poor cardiac autonomic control in the elderly.

Abstract

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 microg/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 ss-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.ImagesFigure 1

Ambient fine particles modify heart rate variability in young healthy adults

“…These studies have found that the elderly with or without cardiovascular conditions, hypertension or diabetes may be more responsive to airborne particle exposure and have a larger reduction of the HRV in relation to an increase in PM 2.5 ambient concentrations (Liao et al, 1999;Pope et al, 1999Pope et al, , 2004bGold et al, 2000;Holguı´n et al, 2003). Our findings are consistent with those even though we studied young healthy adults; as expected, the magnitude of association was larger in those studies where susceptible individuals were included than in ours.…”

“…All of them found that an increase in PM 2.5 or in PM 10 , alone or combined with other pollutants like ozone, were associated with a reduction of the SDNN and of the rMSSD, only one study informed an increase of this last index (Gold et al, 2000). Studies in which frequency domain indexes were used also found this association, particularly of the HF of a parasympathetic-related index (Liao et al, 1999;Holguı´n et al, 2003;Park et al, 2005).…”

“…Other studies have used fixed indoor monitors (Liao et al, 1999;Holguı´n et al, 2003). Outdoor concentrations of PM 2.5 are well correlated with ambient measurements; however, indoor pollutant levels are weekly correlated to outdoor ones.…”

“…Recent studies that included elderly individuals with heart diseases in Baltimore, Boston and Mexico City suggest that PM 2.5 air pollution measured with ambient monitors was associated with a reduced HRV (Liao et al, 1999;Gold et al, 2000;Holguı´n et al, 2003;Park et al, 2005). The aim of this study was to test whether this association could also be observed in young healthy adults, using personal exposure monitors, at ambient levels currently observed in the Mexico City metropolitan area (MCMA).…”

Comparison of PM2.5 and PM10 monitors

“…The National Research Council ( NRC ) has suggested that understanding PM mass concentration measurement errors should be ranked as one of the 10 highest PM research priorities for the U.S. EPA ( NRC, 1998 ). Evaluating the magnitude of this error is important in determining the certainty of epidemiological findings related to matched PM exposure± health effect studies such as those currently being conducted by the U.S. EPA (Liao et al, 1999 ). Quantifying the uncertainties in PM mass measurements made by various monitors would also be useful in comparing exposure data among reported studies.…”