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Author Notes:

Corresponding author: Matthew J. Strickland, PhD, MPH, Assistant Professor, Rollins School of Public Health, Department of Environmental and Occupational Health, 1518 Clifton Road NE, Atlanta, GA 30322, Phone: 404-712-8912, Fax: 404-727-8744, mjstric@sph.emory.edu

Subjects:

Research Funding:

Sources of financial support: National Institute of Environmental Health Sciences grant R01-ES012967-01A1 and Health Resources and Services Administration grant T03MC07651

Keywords:

  • Air Pollution
  • Pregnancy Outcome
  • Confounding Factors (Epidemiology)
  • Research Designs
  • Epidemiologic

The Issue of Confounding in Epidemiological Studies of Ambient Air Pollution and Pregnancy Outcomes

Tools:

Journal Title:

Journal of Epidemiology and Community Health

Volume:

Volume 63, Number 6

Publisher:

, Pages 500-504

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Relationships between ambient air pollution levels during pregnancy and adverse pregnancy outcomes have been investigated using one of three analytic approaches: ambient pollution levels have been contrasted over space, time, or both space and time. Although the three approaches share a common goal, to estimate the causal effects of pollution on pregnancy outcomes, they face different challenges with respect to confounding. In spatial analyses, risk factors that are spatially correlated with pollution levels are confounders; the primary challenges relate to the availability and validity of risk factor measurements. In temporal analyses, where smooth functions of time are commonly used to control for confounding, concerns relate to the adequacy of control and the possibility that abrupt changes in risk might be systematically related to pollution levels. Spatial-temporal approaches are subject to challenges faced in both spatial and temporal analyses. Thoughtful consideration of issues related to confounding is warranted because the causal effects of ambient air pollution on adverse pregnancy outcomes, if they exist, are likely to be small. We present a framework based on counterfactual effect definitions to examine issues related to confounding in spatial, temporal, and spatial-temporal analyses of air pollution and pregnancy outcomes, and we discuss their implications for inference.

Copyright information:

© 2009, British Medical Journal Publishing Group

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