title: Within-person reproducibility of red blood cell mercury over a 10- to 15-year period among women in the Nurses' Health Study II.
abstract: Most epidemiologic studies of methylmercury (MeHg) health effects rely on a single measurement of a MeHg biomarker to assess long-term exposures. Long-term reproducibility data are, therefore, needed to assess the reliability of a single measure to reflect long-term exposures. In this study, we assessed within-person reproducibility of red blood cell (RBC) mercury (Hg), a marker of methyl-mercury, over 10-15 years in a sample of 57 women. Fifty-seven women from the Nurses' Health Study II provided two blood samples 10-15-years apart (median: 12 years), which were analyzed for mercury levels in the red blood cells (B-Hg*). To characterize within-person reproducibility, we estimated correlation and intraclass correlation coefficients (r and ICC) across the two samples. Further, we compared different prediction models, including variables on fish and seafood consumption, for B-Hg* at the first sample, using leave-one-out cross-validation to assess predictive ability. Overall, we observed strong correlations over 10-15 years (r=0.69), as well as a high ICC (0.67; 95% CI: 0.49, 0.79). Fish and seafood consumption reported concurrently with the first B-Hg* sample accounted for 26.8% of the variability in that B-Hg*, giving a correlation of r=0.52. Despite decreasing B-Hg* levels over time, we observed strong correlations and high ICC estimates across B-Hg* measured 10-15 years apart, suggesting good relative within-person stability over time. Our results indicate that a single measurement of B-Hg* likely is adequate to represent long-term exposures.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Marianthi-Anna
authors.initials: MA
authors.lastname: Kioumourtzoglou
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Roberts
authors.affiliation: Department of Environmental Medicine, University of Southern Denmark, Odense, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Nielsen
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA.|Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Shelley S
authors.initials: SS
authors.lastname: Tworoger
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.|Department of Environmental Medicine, University of Southern Denmark, Odense, Denmark.
authors.forename: Philippe
authors.initials: P
authors.lastname: Grandjean
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.|Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Marc G
authors.initials: MG
authors.lastname: Weisskopf
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D015331:Cohort Studies; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D006801:Humans; D008628:Mercury / Q000097:blood*; D008767:Methylmercury Compounds / Q000097:blood; D008875:Middle Aged; D009726:Nurses; D012044:Regression Analysis; D015203:Reproducibility of Results; D017747:Seafood
chemical_list: D015415:Biomarkers; D008767:Methylmercury Compounds; D008628:Mercury