title: Prospective cohort study of lead exposure and electrocardiographic conduction disturbances in the Department of Veterans Affairs Normative Aging Study.
abstract: BACKGROUND
  No studies have examined the association between cumulative low-level lead exposure and the prospective development of electrocardiographic conduction abnormalities, which may mediate the association between lead and several cardiovascular end points.
  
  
  OBJECTIVE
  We prospectively examined the association between lead exposure and the development of electrocardiographic conduction abnormalities.
  
  
  METHODS
  We assessed blood lead, bone lead--a biomarker of cumulative lead exposure--measured with K-shell X-ray fluorescence, and electrocardiographic end points among 600 men in the Normative Aging Study who were free of electrocardiographic abnormalities at the time of the baseline ECG. Of these men, we had follow-up data from a second electrocardiogram for 496 men 8.1 (SD = 3.1) years later, on average. We used repeated measures linear regression to analyze change in electrocardiographic conduction timing and logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for developing specific conduction disturbances and adjusted for potential confounders.
  
  
  RESULTS
  Mean (± SD) blood (5.8 ± 3.6), patella bone (30.3 ± 17.7), and tibia bone (21.6 ± 12.0) lead concentrations were similar to those found in samples from the general U.S. population and much lower than those reported in occupationally exposed groups. Compared with those in the lowest tertile of tibia lead, those in the highest had a 7.94-ms (95% CI, 1.42-14.45) increase in heart rate-corrected QT (QTc) interval and a 5.94-ms increase in heart rate-corrected QRS (95% CI, 1.66-10.22) duration > 8 years. Those in the highest tertile of tibia lead also had increased odds of QT prolongation (QTc ≥ 440 msec; OR = 2.53; 95% CI, 1.22-5.25) and JT prolongation (heart rate-corrected JT > 360 msec; OR = 2.53; 95% CI, 0.93-6.91). Results were weaker for patella lead. No associations were identified with blood lead.
  
  
  CONCLUSIONS
  This study suggests that low-level cumulative exposure to lead is associated with worse future cardiac conductivity in the ventricular myocardium, as reflected in QT interval characteristics.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215, USA.
authors.forename: Ki-Do
authors.initials: KD
authors.lastname: Eum
authors.forename: Linda H
authors.initials: LH
authors.lastname: Nie
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Pantel S
authors.initials: PS
authors.lastname: Vokonas
authors.forename: David
authors.initials: D
authors.lastname: Sparrow
authors.forename: Howard
authors.initials: H
authors.lastname: Hu
authors.forename: Marc G
authors.initials: MG
authors.lastname: Weisskopf
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D001900:Boston / Q000453:epidemiology; D015331:Cohort Studies; D004562:Electrocardiography / Q000187:drug effects*; D006327:Heart Block / Q000139:chemically induced / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D007854:Lead / Q000032:analysis / Q000097:blood; D007855:Lead Poisoning / Q000453:epidemiology*; D016014:Linear Models; D016015:Logistic Models; D008133:Long QT Syndrome / Q000139:chemically induced / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010329:Patella / Q000737:chemistry*; D011446:Prospective Studies; D013977:Tibia / Q000737:chemistry*; D014728:Veterans
chemical_list: D007854:Lead