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Attitude toward livestock farming does not influence the earlier observed association between proximity to goat farms and self-reported pneumonia

Borlée, Floora,b; Yzermans, C. Jorisb; Oostwegel, Floor S. M.a; Schellevis, Françoisb,c; Heederik, Dicka; Smit, Lidwien A. M.a,* VGO Consortium

doi: 10.1097/EE9.0000000000000041
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Background: Attitudes toward environmental risks may be a source of bias in environmental health studies because concerns about environmental hazards may influence self-reported outcomes.

Objective: The main aim was to assess whether earlier observed associations between proximity to goat farms and self-reported pneumonia were biased by participants’ attitude toward farming.

Methods: We developed an attitude-score for 2,457 participants of the Dutch Livestock Farming and Neighbouring Residents’ Health Study (veehouderij en gezondheid omwonenden) by factor analysis of 13 questionnaire items related to attitude toward livestock farming. Linear regression analysis was used to assess associations between attitude and potential determinants. The effect of attitude on the association between goat farm proximity and pneumonia was analyzed by evaluating (1) misclassification of the outcome, (2) effect modification by attitude, and (3) exclusion of participants reporting health problems due to farms in their environment.

Results: In general, the study population had a positive attitude toward farming, especially if participants were more familiar with farming. Older participants, females, ex-smokers, and higher-educated individuals had a more negative attitude. Both self-reported respiratory symptoms and exposure to livestock farms were associated with a more negative attitude. Misclassification of self-reported pneumonia was nondifferential with regard to participants’ attitude. Furthermore, no indication was found that the association between proximity to goat farms and pneumonia was modified by attitude. Excluding subjects who attributed their health symptoms to livestock farms did also not change the association.

Conclusions: The association between goat farm proximity and pneumonia was not substantially biased by study participants’ attitude toward livestock farming.

This is an open access article distributed under the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

aInstitute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands;

bNetherlands Institute for Health Services Research, NIVEL, Utrecht, The Netherlands; and

cDepartment of General Practice & Elderly Care Medicine, Amsterdam Public Health Research Institute, VU University Medical Center, Amsterdam, The Netherlands.

Published online 14 February 2019

Sponsorships or competing interests that may be relevant to content are disclosed at the end of the article.

Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com).

Received: 14 August 2018; Accepted 13 January 2019

*Corresponding author. Address: Institute for Risk Assessment Sciences, Yalelaan 2, 3584 CM, Utrecht, The Netherlands. Tel.: +3130 253 8696. E-mail address: (L. A. M. Smit).

Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc.