title: Individual daytime noise exposure during routine activities and heart rate variability in adults: a repeated measures study.
abstract: BACKGROUND
  Epidemiological studies have demonstrated associations between noise exposure and cardiovascular events. However, there have been few studies of possible underlying mechanisms.
  
  
  OBJECTIVE
  We examined the association between individual daytime noise exposure and heart rate variability (HRV).
  
  
  METHODS
  In a prospective panel study in Augsburg, Germany (March 2007-December 2008), 110 individuals participated in 326 electrocardiogram recordings with a mean duration of 6 hr. Five-minute averages of heart rate (HR) and HRV parameters were determined. Individual noise exposure was measured as A-weighted equivalent continuous sound pressure levels (L(eq)). Effects were estimated using additive mixed models adjusted for long- and short-term time trends and physical activity. Due to nonlinear exposure-response functions, we performed piecewise linear analyses with a cut-off point at 65 dB(A).
  
  
  RESULTS
  Concurrent increases of 5 dB(A) in L(eq) < 65 dB(A) were associated with increases in HR (percent change of mean value: 1.48%; 95% CI: 1.37, 1.60%) and the ratio of low-frequency (LF) to high-frequency (HF) power (4.89%; 95% CI: 3.48, 6.32%), and with decreases in LF (-3.77%; 95% CI: -5.49, -2.02%) and HF (-8.56%; 95% CI: -10.31, -6.78%) power. Standard deviation of normal-to-normal intervals (SDNN) was positively associated with concurrent noise < 65 dB(A) (5.74%; 95% CI: 5.13, 6.36) but negatively associated with noise lagged by 5-15 min (-0.53% to -0.69%). Associations with cardiac function were less pronounced for noise ≥ 65 dB(A), with some in opposite directions from associations with noise < 65 dB(A). Concurrent associations were modified by sex and age.
  
  
  CONCLUSIONS
  Individual daytime noise exposure was associated with immediate changes in HRV, suggesting a possible mechanism linking noise to cardiovascular risk. Noise at lower levels may have health consequences beyond those resulting from "fight-or-flight" responses to high levels of noise.
authors.affiliation: Institute of Epidemiology II, Helmholtz Zentrum München, Neuherberg, Germany. ute.kraus@helmholtz-muenchen.de
authors.forename: Ute
authors.initials: U
authors.lastname: Kraus
authors.forename: Alexandra
authors.initials: A
authors.lastname: Schneider
authors.forename: Susanne
authors.initials: S
authors.lastname: Breitner
authors.forename: Regina
authors.initials: R
authors.lastname: Hampel
authors.forename: Regina
authors.initials: R
authors.lastname: Rückerl
authors.forename: Mike
authors.initials: M
authors.lastname: Pitz
authors.forename: Uta
authors.initials: U
authors.lastname: Geruschkat
authors.forename: Petra
authors.initials: P
authors.lastname: Belcredi
authors.forename: Katja
authors.initials: K
authors.lastname: Radon
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
mesh_terms: D000328:Adult; D000368:Aged; D004562:Electrocardiography; D004781:Environmental Exposure; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects*; D011446:Prospective Studies