title: Modifying effect of a common polymorphism in the interleukin-6 promoter on the relationship between long-term exposure to traffic-related particulate matter and heart rate variability.
abstract: BACKGROUND
  Exposure to particulate matter (PM) has been associated with an increase in many inflammatory markers, including interleukin 6 (IL6). Air pollution exposure has also been suggested to induce an imbalance in the autonomic nervous system (ANS), such as a decrease in heart rate variability (HRV). In this study we aimed to investigate the modifying effect of polymorphisms in a major proinflammatory marker gene, interleukin 6 (IL6), on the relationship between long-term exposure to traffic-related PM10 (TPM10) and HRV.
  
  
  METHODS
  For this cross-sectional study we analysed 1552 participants of the SAPALDIA cohort aged 50 years and older. Included were persons with valid genotype data, who underwent ambulatory 24-hr electrocardiogram monitoring, and reported on medical history and lifestyle. Main effects of annual average TPM10 and IL6 gene variants (rs1800795; rs2069827; rs2069840; rs10242595) on HRV indices and their interaction with average annual exposure to TPM10 were tested, applying a multivariable mixed linear model.
  
  
  RESULTS
  No overall association of TPM10 on HRV was found. Carriers of two proinflammatory G-alleles of the functional IL6 -174 G/C (rs1800795) polymorphism exhibited lower HRV. An inverse association between a 1 µg/m3 increment in yearly averaged TPM10 and HRV was restricted to GG genotypes at this locus with a standard deviation of normal-to-normal intervals (SDNN) (GG-carriers: -1.8%; 95% confidence interval -3.5 to 0.01; pinteraction(additive) = 0.028); and low frequency power (LF) (GG-carriers: -5.7%; 95%CI: -10.4 to -0.8; pinteraction(dominant) = 0.049).
  
  
  CONCLUSIONS
  Our results are consistent with the hypothesis that traffic-related air pollution decreases heart rate variability through inflammatory mechanisms.
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Adam
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Medea
authors.initials: M
authors.lastname: Imboden
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland; Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Boes
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Schaffner
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Harish Chandra
authors.initials: HC
authors.lastname: Phuleria
authors.affiliation: Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Kronenberg
authors.affiliation: Department of Community Medicine, Primary Care and Emergency medicine, University Hospitals, Geneva, Switzerland.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Gaspoz
authors.affiliation: Cardiology, Department of Internal Medicine Specialties, University Hospitals, Geneva, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Carballo
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors.forename: Nicole
authors.initials: N
authors.lastname: Probst-Hensch
mesh_terms: D000368:Aged; D001341:Autonomic Nervous System / Q000187:drug effects / Q000378:metabolism; D003430:Cross-Sectional Studies; D004562:Electrocardiography; D005260:Female; D005838:Genotype; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000633:toxicity*; D011110:Polymorphism, Genetic / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*
chemical_list: D015850:Interleukin-6; D052638:Particulate Matter