title: Air pollution and heart rate variability among the elderly in Mexico City.
abstract: 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.
mesh_terms: 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
chemical_list: D000393:Air Pollutants; D013458:Sulfur Dioxide; D010126:Ozone; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide