Document Detail

Defining exposure in case-control studies: a new approach.
MedLine Citation:
PMID:  2035506     Owner:  NLM     Status:  MEDLINE    
Many epidemiologists conducting case-control studies choose to dichotomize their exposure data to make the analysis of the data easier and its presentation more straightforward. The choice of a specific rule for dichotomization can have a large effect on the outcome measure, the odds ratio, although this effect is rarely studied. The authors present a graphic approach for exploring this effect, the quantile-quantile (Q-Q) plot. By examining a Q-Q plot, an investigator simultaneously gains information about the distribution of exposures among cases, the distribution of exposures among controls, and odds ratios at all possible cutpoints and their standard errors. In addition, by finding the slope at each point along the Q-Q curve, it is possible to estimate the rate ratios for each possible value of exposure. The authors view the use of the Q-Q plot as an exploratory tool. It enables the investigator to become more familiar with the data and check for irregularities such as outliers, nonlinearities, or nonmonotonic dose-response curves, and idiosyncratic variations of the odds ratio. The authors present an example evaluating the risk of low birth weight as a function of mother's age for Boston births in 1984.
D Wartenberg; M Northridge
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of epidemiology     Volume:  133     ISSN:  0002-9262     ISO Abbreviation:  Am. J. Epidemiol.     Publication Date:  1991 May 
Date Detail:
Created Date:  1991-06-21     Completed Date:  1991-06-21     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7910653     Medline TA:  Am J Epidemiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1058-71     Citation Subset:  IM    
Department of Environmental and Community Medicine, University of Medicine & Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854.
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MeSH Terms
Case-Control Studies*
Confounding Factors (Epidemiology)
Data Interpretation, Statistical*
Environmental Exposure
Infant, Low Birth Weight
Infant, Newborn
Maternal Age
Middle Aged
Odds Ratio
Risk Factors
Grant Support
U50/CCU101045-04//PHS HHS
Comment In:
Am J Epidemiol. 1992 Nov 15;136(10):1294   [PMID:  1476152 ]
Am J Epidemiol. 1994 Feb 15;139(4):442-5   [PMID:  8109578 ]

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

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