Article

The effect of lipid adjustment on the analysis of environmental contaminants and the outcome of human health risks.

Division of Epidemiology, Statistics and Prevention Research, Eunice Kennedy Schriver National Institute of Child Health and Human Development, NIH, Rockville, MD, USA.
Methods in molecular biology (Clifton, N.J.) (Impact Factor: 1.29). 01/2009; 580:371-81. DOI: 10.1007/978-1-60761-325-1_20
Source: PubMed

ABSTRACT Past literature on exposure to lipophilic agents such as organochlorines (OCs) is conflicting, posing challenges for the interpretation of their potential human health risks. Since blood is often used as a proxy for adipose tissue, it is necessary to model serum lipids when assessing health risks of OCs. Using a simulation study, we evaluated four statistical models (unadjusted, standardized, adjusted, and two-stage) for the analysis of polychlorinated biphenyls (PCBs) exposure, serum lipids, and health outcome risk. Eight candidate true causal scenarios, depicted by directed acyclic graphs, were used to illustrate the ramifications of misspecification of underlying assumptions when interpreting results. Biased results were produced when statistical models that deviated from the underlying causal assumptions were used with the lipid standardization method found to be particularly prone to bias. We concluded that investigators must consider biology, biological medium, laboratory measurement, and other underlying modeling assumptions when devising a statistical model for assessing health outcomes in relation to environmental exposures.

0 Bookmarks
 · 
86 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Organochlorine pesticides (OCPs) have been linked to adult metabolic disorders; however, few studies have examined these associations in childhood. We prospectively evaluated the associations of baseline serum OCPs (hexachlorobenzene, β-hexachlorocyclohexane, and p,p′-dichlorodiphenyldichloroethylene) in Russian boys with subsequent repeated measurements of serum glucose, insulin, lipids, leptin, and calculated homeostatic model assessment of insulin resistance (IR). During 2003–2005, we enrolled 499 boys aged 8–9 years in a prospective cohort; 318 had baseline serum OCPs and serum biomarkers measured at ages 10–13 years. Multivariable generalized estimating equation and mediation regression models were used to examine associations and direct and indirect (via body mass index (BMI) (weight (kg)/height (m)2)) effects of prepubertal OCP tertiles and quintiles with biomarkers. In multivariable models, higher p,p′-dichlorodiphenyldichloroethylene (quintile 5 vs. quintile 1) was associated with lowe
    American Journal of Epidemiology 09/2014; · 4.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this research was to study the association of the accumulated human exposure to persistent organic pollutants with serum lipid levels and obesity, in a cohort of 298 adults. In the multivariable analyses, HCB concentrations evidenced a significant quadratic association with levels of total cholesterol, HDL, LDL, and total serum lipids. Likewise, PCBs 138 and 180 were associated with triglycerides and total serum lipids, and PCB 153 with LDL. HCB, p,p'-DDE, and β-HCH showed quadratic associations with BMI. All quadratic models showed a positive trend at low exposure levels, while the slope decreased or even became negative at higher exposure levels. Additionally, PCB 138 was positively associated with BMI but in a linear manner. Our results suggest a potential relationship between historical POP exposure and serum lipids/obesity, which followed a non-linear pattern in most cases.
    Environmental Pollution 08/2014; 195C:9-15. · 3.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polybrominated diphenyl ethers (PBDEs) are flame retardant chemicals used in consumer products. They are common contaminants in human serum and associated with adverse health effects. Our objectives were to characterize PBDE serum concentrations in a New England cohort and assess temporal variability of this exposure biomarker over a one-year period. We collected three repeated measurements at six-month intervals from 52 office workers from the greater Boston (USA) area from 2010 to 2011. The intraclass correlation coefficient for BDEs 28, 47, 99, 100 and 153 ranged from 0.87 to 0.99, indicating that a single serum measurement can reliably estimate exposure over a one-year period. This was true for both lipid adjusted and non-lipid adjusted concentrations. The kappa statistics, quantifying the level of agreement of categorical exposure classification, based on medians, tertiles, or quartiles ranged from 0.67 to 0.90. Some congeners showed non-significant increases from sampling round 1 (winter) to round 2 (summer) and significant decreases from round 2 to round 3 (winter). This study highlights the high reliability of a single serum PBDE measurement for use in human epidemiologic studies.
    Environmental science & technology. 11/2014;

Full-text (2 Sources)

Download
7 Downloads
Available from
Sep 10, 2014