title: Heart rate variability associated with particulate air pollution.
abstract: BACKGROUND
  Epidemiologic studies have linked fine particulate air pollution with cardiopulmonary mortality, yet underlying biologic mechanisms remain unknown. Changes in heart rate variability (HRV) may reflect changes in cardiac autonomic function and risk of sudden cardiac death. This study evaluated changes in mean heart rate and HRV in human beings associated with changes in exposure to particulate air pollution.
  
  
  METHODS
  Repeated ambulatory electrocardiographic monitoring was conducted on 7 subjects for a total of 29 person-days before, during, and after episodes of elevated pollution. Mean HR, the standard deviation of normal-to-normal (NN) intervals (SDNN), the standard deviation of the averages of NN intervals in all 5-minute segments of the recording (SDANN), and the square root of the mean of squared differences between adjacent NN intervals (r-MSSD) were calculated for 24-hour and 6-hour time segments. Associations of HRV with particulate pollution levels were evaluated with fixed-effects regression models.
  
  
  RESULTS
  After controlling for differences across patients, elevated particulate levels were associated with (1) increased mean HR, (2) decreased SDNN, a measure of overall HRV, (3) decreased SDANN, a measure that corresponds to ultralow frequency variability, and (4) increased r-MSSD, a measure that corresponds to high-frequency variability. The associations between HRV and particulates were small but persisted even after controlling for mean HR.
  
  
  CONCLUSIONS
  This study suggests that changes in cardiac autonomic function reflected by changes in mean HR and HRV may be part of the pathophysiologic mechanisms or pathways linking cardiovascular mortality and particulate air pollution.
authors.affiliation: Brigham Young University, Provo, Utah, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Pope
authors.forename: R L
authors.initials: RL
authors.lastname: Verrier
authors.forename: E G
authors.initials: EG
authors.lastname: Lovett
authors.forename: A C
authors.initials: AC
authors.lastname: Larson
authors.forename: M E
authors.initials: ME
authors.lastname: Raizenne
authors.forename: R E
authors.initials: RE
authors.lastname: Kanner
authors.forename: J
authors.initials: J
authors.lastname: Schwartz
authors.forename: G M
authors.initials: GM
authors.lastname: Villegas
authors.forename: D R
authors.initials: DR
authors.lastname: Gold
authors.forename: D W
authors.initials: DW
authors.lastname: Dockery
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000397:Air Pollution / Q000009:adverse effects*; D001341:Autonomic Nervous System / Q000503:physiopathology; D002318:Cardiovascular Diseases / Q000209:etiology / Q000401:mortality* / Q000503:physiopathology; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000294:innervation / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D011795:Surveys and Questionnaires; D014589:Utah / Q000453:epidemiology