Air pollution and heart rate variability among the elderly in Mexico City.
BACKGROUND
Suspended particles and ozone have been associated with varying degrees of cardiac autonomic dysfunction.


METHODS
In Mexico City, residents from a nursing home underwent heart rate variability analysis every other day for 3 months. Indoor and outdoor PM2.5 (particulate matter less than 2.5 mm in diameter) were measured daily at the nursing home. Levels of ozone and other atmospheric pollutants were obtained from a nearby automated monitoring station.


RESULTS
Of the initial 42 screened participants, 34 (81%) were followed during the study period. The 24-hour average levels of indoor PM2.5 ranged from 15 to 67 micro g/m3, and outdoor PM2.5 ranged from 9 to 87 micro g/m3. Daily 1-hour maximum ozone levels ranged from 47 to 228 ppb. After adjusting for age and heart rate, we observed a strong decrease in the high frequency component of heart rate variability and the average 24-hour concentrations of PM2.5. Participants with hypertension had considerably larger reductions in their HF-HRV (high frequency-heart rate variability) component in relation to both ozone and PM2.5 exposure.


CONCLUSIONS
Our results suggest that ambient levels of PM2.5 and ozone can reduce the high-frequency component of heart rate variability in elderly subjects living in Mexico City and that subjects with underlying hypertension are particularly susceptible to this effect.
D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000633:toxicity*; D002248:Carbon Monoxide / Q000032:analysis; D002318:Cardiovascular Diseases / Q000209:etiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis; D009735:Nursing Homes; D010126:Ozone / Q000032:analysis; D010316:Particle Size; D013458:Sulfur Dioxide / Q000032:analysis
D000393:Air Pollutants; D013458:Sulfur Dioxide; D010126:Ozone; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide