Selection bias in ecological studies.

TitreSelection bias in ecological studies.
Publication TypeJournal Article
Year of Publication2017
AuthorsRousson, V, Rosselet, P, Paccaud, F
JournalPublic Health
Volume153
Pagination103-106
Date Published10/2017
DOI10.1016/j.puhe.2017.09.001
ISSN1476-5616
Abstract

An ecological study is an observational epidemiological study which uses aggregated data instead of individual data, where the aggregation is usually done at some geographical level such as a town, a region, or a country.1 They are typically carried out when an exposure of interest is fully defined at the group level.2 A classical example is the association between air pollution and a specific health outcome. While it is difficult (or even meaningless) to measure individual exposure to air pollution, it is easier to measure air quality in a region. In order to investigate the association between air pollution and the occurrence of some disease, one may correlate the available measures of air quality with the prevalence (or incidence) of the disease over a set of regions. This approach faces several limitations; in the literature about ecological studies, one can find numerous warnings against the ‘ecological fallacy’, which states that a correlation at the group level is not of the same magnitude (and not always with the same sign) than a correlation at the individual level,3 and about confounding.4 The present communication aims to be a reminder about another serious limitation of ecological studies which is rarely mentioned in the literature: selection bias. Yet, as illustrated below, a deception due to a selection bias might be still more spectacular than any confounding issue.

Alternate URL

http://www.ncbi.nlm.nih.gov/pubmed/28988147?dopt=Abstract

WOS ID (UT)

000416741400016

Alternate JournalPublic Health
Citation Key / SERVAL ID8282
Peer reviewRefereed
PubMed ID28988147

                         

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