Ambient AIr Pollution and Heart Rate Variability (Hrv) in Two Sensitive Populations

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ISEE-38 Introduction. Significant associations between ambient fine particle (PM2.5) concentrations and decreased heart rate variability (HRV) have been shown in epidemiological studies. To examine further the effects of ambient pollution concentrations on HRV, a cardiovascular health study was conducted in Atlanta, GA during Fall 1999 and Spring 2000. Methods. Holter monitoring was conducted for 31 individuals living in metropolitan Atlanta, 19 of which had chronic obstructive pulmonary disease (COPD) and 12 had recent MIs. Each participant was monitored on seven days in either or both the fall and spring seasons. Holter data were analyzed for measures of HRV. Hourly ambient pollution concentrations were obtained from stationary ambient monitoring (SAM) sites in Atlanta. The association between ambient pollution and log-transformed HRV was examined using linear mixed effects models (LME). Models controlled for subject as a random effect, body mass index, gender, age, medication use, season, temperature, relative humidity, hour and day of week. Models were also run including baseline FEV1 as interaction terms. Results were scaled by an inter-quartile range (IQR) increase in ambient PM2.5 (10.6 ug/m3) and EC (1.2 ug/m3). Results. Disease status or lung function level modified the associations of 4-hour mean ambient pollution with HRV. Increased pollution levels were associated with increased HRV for those with COPD or marked airway obstruction, and with no change or decreases in HRV for those with MI diagnosis or normal lung function levels. For individuals with COPD, the standard deviation of normal RR intervals (SDNN) rose by 7.5% (95% CI: 1.5–13.9%) per IQR increase in ambient PM2.5. Similarly for those with marked airway obstruction (a subset of those with COPD; baseline FEV1=35% of predicted), an IQR increase in 4-h ambient PM2.5 was associated with a 10.2% (95% CI: 3.8–17.0%) increase in SDNN. In contrast, those with MI and/or with normal FEV1 percent predicted had a small, not statistically significant decrease in SDNN in response to PM2.5. For 24-h ambient EC, SDNN decreased significantly by 4.9% (95% CI: −8.7 to −1.0%) per IQR increase in persons with a normal baseline FEV1, while subjects with an FEV1 of only 35% of predicted showed an insignificant 2.9% increase (95% CI: −1.2 to 7.1%) in SDNN per the same IQR increase in ambient EC. Discussion. Results suggest that the association between ambient air pollution and HRV varies with either disease status or baseline pulmonary function. Further research should be conducted to determine whether this association is generalizable to other study populations.