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Confounding in air pollution epidemiology: when does two-stage regression identify the problem?
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MedLine Citation:
PMID:  11748025     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A two-stage approach has recently been proposed to assess confounding by copollutants or other variables in time-series epidemiology studies for airborne particulate matter (PM), using independent series from different cities. In the first stage of the proposed method, two regression models are fitted for each city in the analysis. The first relates the health effect to the putative causal variable such as PM without including any copollutant or confounder. The other first-stage model relates a putative confounding variable to PM. In the second stage of the analysis, the estimated city-specific regression slopes for the health-effect-versus-PM model are regressed against the estimated city-specific regression slopes for the confounder-versus-PM model. Under the proposed method, a nonzero intercept estimate in the second-stage regression would be interpreted as indicating a direct pathway from PM to the health effect, and a nonzero slope estimate would be interpreted as indicating at least partial confounding of PM with the putative confounder. A simple counterexample using an additional copollutant variable shows that inferences based on this method could be misleading.
Authors:
A H Marcus; S R Kegler
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Environmental health perspectives     Volume:  109     ISSN:  0091-6765     ISO Abbreviation:  Environ. Health Perspect.     Publication Date:  2001 Dec 
Date Detail:
Created Date:  2001-12-18     Completed Date:  2002-02-05     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0330411     Medline TA:  Environ Health Perspect     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1193-6     Citation Subset:  IM    
Affiliation:
National Center for Environmental Assessment - RTP, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA. marcus.allan@epa.gov
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MeSH Terms
Descriptor/Qualifier:
Air Pollutants / adverse effects*
Confounding Factors (Epidemiology)
Epidemiologic Studies
Humans
Models, Theoretical
Particle Size
Public Health
Regression Analysis*
Chemical
Reg. No./Substance:
0/Air Pollutants
Comments/Corrections

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Full Text
Journal Information
Journal ID (nlm-ta): Environ Health Perspect
ISSN: 0091-6765
Article Information
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Print publication date: Month: 12 Year: 2001
Volume: 109 Issue: 12
First Page: 1193 Last Page: 1196
ID: 1240500
PubMed Id: 11748025
Publisher Item Identifier: sc271_5_1835

Confounding in air pollution epidemiology: when does two-stage regression identify the problem?
A H Marcus
S R Kegler
National Center for Environmental Assessment - RTP, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA. marcus.allan@epa.gov


Article Categories:
  • Research Article


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