Determinants of citation in the literature on diesel exhaust exposure and lung cancer: a citation analysis

Bram Duyx; Miriam J. E. Urlings; Gerard M. H. Swaen; Lex M. Bouter; Maurice P. Zeegers

doi:10.1136/bmjopen-2019-033967

Determinants of citation in the literature on diesel exhaust exposure and lung cancer: a citation analysis

Bram Duyx^*, Miriam J. E. Urlings, Gerard M. H. Swaen, Lex M. Bouter, Maurice P. Zeegers

^*Corresponding author for this work

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Objectives Epidemiological research on the association between diesel exhaust exposure and lung cancer risk has some methodological challenges that give rise to different conclusions and intense debates. This raises the question about the role of selective citation and of citation bias in particular. Our aim was to investigate the occurrence and prevalence of selective citation in this field. Design Citation analysis. Setting Web of Science Core Collection. Participants We identified 96 publications in this network, with 4317 potential citations. For each publication, we extracted characteristics such as study conclusion and funding source. Some of these characteristics are related to the study content: study design, sample size, method of diesel exposure assessment, type of diesel technology under investigation, and whether smoking had been adjusted for. Primary and secondary outcome measures Whether a citation occurs or not, measured and analysed according to the preregistered protocol. Exploratively we analysed the association between funding source and study conclusion. Results Methodological content of a study was clearly related to citation, studies using more sophisticated methods were more likely to be cited. There was some evidence for citation bias: supportive publications had a higher chance of being cited than non-supportive ones, but after adjustment for study quality, this effect decreased substantially (adjusted OR 1.3, 95% CI 1.0 to 1.7). Explorative analyses indicated that three quarters of non-profit funded publications had a supportive study conclusion against only one quarter of the industry-funded publications. Conclusions There is evidence for selective citation within this field, but the evidence for citation bias was weak. It seems that factors related to the methodology had more impact on citation than the conclusion of a study. Interestingly, publications that were funded by industry were more skeptical about a causal relationship between diesel exhaust and lung cancer compared to non-profit-funded publications.

Original language	English
Article number	033967
Number of pages	11
Journal	BMJ Open
Volume	10
Issue number	10
DOIs	https://doi.org/10.1136/bmjopen-2019-033967
Publication status	Published - 2020

Keywords

selective citation
citation bias
diesel exhaust
lung cancer
funding source
CARDIOVASCULAR CLINICAL-TRIALS
ENGINE EXHAUST
BIAS
PUBLICATION
CARCINOGENICITY
PATTERNS
OUTCOMES
SMOKING
RATES

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10.1136/bmjopen-2019-033967Licence: CC BY-NC

Cite this

@article{6680f3c2e8aa4aff8f128e2ec3743c53,

title = "Determinants of citation in the literature on diesel exhaust exposure and lung cancer: a citation analysis",

abstract = "Objectives Epidemiological research on the association between diesel exhaust exposure and lung cancer risk has some methodological challenges that give rise to different conclusions and intense debates. This raises the question about the role of selective citation and of citation bias in particular. Our aim was to investigate the occurrence and prevalence of selective citation in this field. Design Citation analysis. Setting Web of Science Core Collection. Participants We identified 96 publications in this network, with 4317 potential citations. For each publication, we extracted characteristics such as study conclusion and funding source. Some of these characteristics are related to the study content: study design, sample size, method of diesel exposure assessment, type of diesel technology under investigation, and whether smoking had been adjusted for. Primary and secondary outcome measures Whether a citation occurs or not, measured and analysed according to the preregistered protocol. Exploratively we analysed the association between funding source and study conclusion. Results Methodological content of a study was clearly related to citation, studies using more sophisticated methods were more likely to be cited. There was some evidence for citation bias: supportive publications had a higher chance of being cited than non-supportive ones, but after adjustment for study quality, this effect decreased substantially (adjusted OR 1.3, 95% CI 1.0 to 1.7). Explorative analyses indicated that three quarters of non-profit funded publications had a supportive study conclusion against only one quarter of the industry-funded publications. Conclusions There is evidence for selective citation within this field, but the evidence for citation bias was weak. It seems that factors related to the methodology had more impact on citation than the conclusion of a study. Interestingly, publications that were funded by industry were more skeptical about a causal relationship between diesel exhaust and lung cancer compared to non-profit-funded publications.",

keywords = "selective citation, citation bias, diesel exhaust, lung cancer, funding source, CARDIOVASCULAR CLINICAL-TRIALS, ENGINE EXHAUST, BIAS, PUBLICATION, CARCINOGENICITY, PATTERNS, OUTCOMES, SMOKING, RATES",

author = "Bram Duyx and Urlings, {Miriam J. E.} and Swaen, {Gerard M. H.} and Bouter, {Lex M.} and Zeegers, {Maurice P.}",

note = "Funding Information: χ2(2)=9.2, p=0.01. Non-supportive conclusion includes publications that concluded no association or an unclear association. Seven publications (six exclusively non-profit and one with combined funding) did not state a clear conclusion and were excluded from these analyses, as were the two (exclusively non-profit) publications that had reached a mixed conclusion. Publications that failed to report their funding source were also excluded. Three of the for-profit publications were funded by financial institutions, all the other ones by the transport industry. Only one of the publications funded by the transport industry had reached a supportive conclusion. Publisher Copyright: {\textcopyright} ",

year = "2020",

doi = "10.1136/bmjopen-2019-033967",

language = "English",

volume = "10",

journal = "BMJ Open",

issn = "2044-6055",

publisher = "BMJ Publishing Group",

number = "10",

}

TY - JOUR

T1 - Determinants of citation in the literature on diesel exhaust exposure and lung cancer

T2 - a citation analysis

AU - Duyx, Bram

AU - Urlings, Miriam J. E.

AU - Swaen, Gerard M. H.

AU - Bouter, Lex M.

AU - Zeegers, Maurice P.

N1 - Funding Information: χ2(2)=9.2, p=0.01. Non-supportive conclusion includes publications that concluded no association or an unclear association. Seven publications (six exclusively non-profit and one with combined funding) did not state a clear conclusion and were excluded from these analyses, as were the two (exclusively non-profit) publications that had reached a mixed conclusion. Publications that failed to report their funding source were also excluded. Three of the for-profit publications were funded by financial institutions, all the other ones by the transport industry. Only one of the publications funded by the transport industry had reached a supportive conclusion. Publisher Copyright: ©

PY - 2020

Y1 - 2020

N2 - Objectives Epidemiological research on the association between diesel exhaust exposure and lung cancer risk has some methodological challenges that give rise to different conclusions and intense debates. This raises the question about the role of selective citation and of citation bias in particular. Our aim was to investigate the occurrence and prevalence of selective citation in this field. Design Citation analysis. Setting Web of Science Core Collection. Participants We identified 96 publications in this network, with 4317 potential citations. For each publication, we extracted characteristics such as study conclusion and funding source. Some of these characteristics are related to the study content: study design, sample size, method of diesel exposure assessment, type of diesel technology under investigation, and whether smoking had been adjusted for. Primary and secondary outcome measures Whether a citation occurs or not, measured and analysed according to the preregistered protocol. Exploratively we analysed the association between funding source and study conclusion. Results Methodological content of a study was clearly related to citation, studies using more sophisticated methods were more likely to be cited. There was some evidence for citation bias: supportive publications had a higher chance of being cited than non-supportive ones, but after adjustment for study quality, this effect decreased substantially (adjusted OR 1.3, 95% CI 1.0 to 1.7). Explorative analyses indicated that three quarters of non-profit funded publications had a supportive study conclusion against only one quarter of the industry-funded publications. Conclusions There is evidence for selective citation within this field, but the evidence for citation bias was weak. It seems that factors related to the methodology had more impact on citation than the conclusion of a study. Interestingly, publications that were funded by industry were more skeptical about a causal relationship between diesel exhaust and lung cancer compared to non-profit-funded publications.

AB - Objectives Epidemiological research on the association between diesel exhaust exposure and lung cancer risk has some methodological challenges that give rise to different conclusions and intense debates. This raises the question about the role of selective citation and of citation bias in particular. Our aim was to investigate the occurrence and prevalence of selective citation in this field. Design Citation analysis. Setting Web of Science Core Collection. Participants We identified 96 publications in this network, with 4317 potential citations. For each publication, we extracted characteristics such as study conclusion and funding source. Some of these characteristics are related to the study content: study design, sample size, method of diesel exposure assessment, type of diesel technology under investigation, and whether smoking had been adjusted for. Primary and secondary outcome measures Whether a citation occurs or not, measured and analysed according to the preregistered protocol. Exploratively we analysed the association between funding source and study conclusion. Results Methodological content of a study was clearly related to citation, studies using more sophisticated methods were more likely to be cited. There was some evidence for citation bias: supportive publications had a higher chance of being cited than non-supportive ones, but after adjustment for study quality, this effect decreased substantially (adjusted OR 1.3, 95% CI 1.0 to 1.7). Explorative analyses indicated that three quarters of non-profit funded publications had a supportive study conclusion against only one quarter of the industry-funded publications. Conclusions There is evidence for selective citation within this field, but the evidence for citation bias was weak. It seems that factors related to the methodology had more impact on citation than the conclusion of a study. Interestingly, publications that were funded by industry were more skeptical about a causal relationship between diesel exhaust and lung cancer compared to non-profit-funded publications.

KW - selective citation

KW - citation bias

KW - diesel exhaust

KW - lung cancer

KW - funding source

KW - CARDIOVASCULAR CLINICAL-TRIALS

KW - ENGINE EXHAUST

KW - BIAS

KW - PUBLICATION

KW - CARCINOGENICITY

KW - PATTERNS

KW - OUTCOMES

KW - SMOKING

KW - RATES

U2 - 10.1136/bmjopen-2019-033967

DO - 10.1136/bmjopen-2019-033967

M3 - Article

C2 - 33033008

SN - 2044-6055

VL - 10

JO - BMJ Open

JF - BMJ Open

IS - 10

M1 - 033967

ER -