title: Associations between PM2.5 and heart rate variability are modified by particle composition and beta-blocker use in patients with coronary heart disease.
abstract: BACKGROUND
  It has been hypothesized that ambient particulate air pollution is able to modify the autonomic nervous control of the heart, measured as heart rate variability (HRV). Previously we reported heterogeneous associations between particulate matter with aerodynamic diameter < 2.5 microm (PM2.5) and HRV across three study centers.
  
  
  OBJECTIVE
  We evaluated whether exposure misclassification, effect modification by medication, or differences in particle composition could explain the inconsistencies.
  
  
  METHODS
  Subjects with coronary heart disease visited clinics biweekly in Amsterdam, the Netherlands; Erfurt, Germany; and Helsinki, Finland for 6-8 months. The standard deviation (SD) of NN intervals on an electrocardiogram (ECG; SDNN) and high frequency (HF) power of HRV was measured with ambulatory ECG during paced breathing. Outdoor levels of PM2.5 were measured at a central site. In Amsterdam and Helsinki, indoor and personal PM2.5 were measured during the 24 hr preceding the clinic visit. PM2.5 was apportioned between sources using principal component analyses. We analyzed associations of indoor/personal PM2.5, elements of PM2.5, and source-specific PM2.5 with HRV using linear regression.
  
  
  RESULTS
  Indoor and personal PM2.5 were not associated with HRV. Increased outdoor PM2.5 was associated with decreased SDNN and HF at lags of 2 and 3 days only among persons not using beta-blocker medication. Traffic-related PM2.5 was associated with decreased SDNN, and long-range transported PM2.5 with decreased SDNN and HF, most strongly among persons not using beta blockers. Indicators for PM2.5 from traffic and long-range transport were also associated with decreased HRV.
  
  
  CONCLUSIONS
  Our results suggest that differences in the composition of particles, beta-blocker use, and obesity of study subjects may explain some inconsistencies among previous studies on HRV.
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands. J.J.deHartog@uu.nl
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: de Hartog
authors.forename: Timo
authors.initials: T
authors.lastname: Lanki
authors.forename: Kirsi L
authors.initials: KL
authors.lastname: Timonen
authors.forename: Gerard
authors.initials: G
authors.lastname: Hoek
authors.forename: Nicole A H
authors.initials: NA
authors.lastname: Janssen
authors.forename: Angela
authors.initials: A
authors.lastname: Ibald-Mulli
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.forename: Joachim
authors.initials: J
authors.lastname: Heinrich
authors.forename: Tuula H
authors.initials: TH
authors.lastname: Tarkiainen
authors.forename: Rene
authors.initials: R
authors.lastname: van Grieken
authors.forename: Joop H
authors.initials: JH
authors.lastname: van Wijnen
authors.forename: Bert
authors.initials: B
authors.lastname: Brunekreef
authors.forename: Juha
authors.initials: J
authors.lastname: Pekkanen
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology* / Q000627:therapeutic use*; D000328:Adult; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010316:Particle Size
chemical_list: D000319:Adrenergic beta-Antagonists