title: Mercury Exposure and Heart Rate Variability: a Systematic Review.
abstract: BACKGROUND
  Mercury affects the nervous system and has been implicated in altering heart rhythm and function. We sought to better define its role in modulating heart rate variability, a well-known marker of cardiac autonomic function.
  
  
  METHODS
  This is a systematic review study.
  
  
  METHODS
  We searched PubMed, Embase, TOXLINE, and DART databases without language restriction. We report findings as a qualitative systematic review because heterogeneity in study design and assessment of exposures and outcomes across studies, as well as other methodological limitations of the literature, precluded a quantitative meta-analysis.
  
  
  RESULTS
  We identified 12 studies of mercury exposure and heart rate variability in human populations (ten studies involving primarily environmental methylmercury exposure and two studies involving occupational exposure to inorganic mercury) conducted in Japan, the Faroe Islands, Canada, Korea, French Polynesia, Finland, and Egypt. The association of prenatal mercury exposure with lower high-frequency band scores (thought to reflect parasympathetic activity) in several studies, in particular the inverse association of cord blood mercury levels with the coefficient of variation of the R-R intervals and with low-frequency and high-frequency bands at 14 years of age in the Faroe Islands birth cohort study, suggests that early mercury exposure could have a long-lasting effect on cardiac parasympathetic activity. Studies with later environmental exposures to mercury in children or in adults were heterogeneous and did not show consistent associations.
  
  
  CONCLUSIONS
  The evidence was too limited to draw firm causal inferences. Additional research is needed to elucidate the effects of mercury on cardiac autonomic function, particularly as early-life exposures might have lasting impacts on cardiac parasympathetic function.
authors.affiliation: Department of Preventive Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Matthew O
authors.initials: MO
authors.lastname: Gribble
authors.forename: Alan
authors.initials: A
authors.lastname: Cheng
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
authors.forename: Lori
authors.initials: L
authors.lastname: Rosman
authors.forename: Eliseo
authors.initials: E
authors.lastname: Guallar
mesh_terms: D000293:Adolescent; D000328:Adult; D001341:Autonomic Nervous System / Q000187:drug effects / Q000503:physiopathology; D002648:Child; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008628:Mercury / Q000633:toxicity*; D020262:Mercury Poisoning, Nervous System; D016273:Occupational Exposure / Q000032:analysis; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000503:physiopathology
chemical_list: D008628:Mercury