Determinants of Citation in Epidemiological Studies on Phthalates:A Citation Analysis

Citing of previous publications is an important factor in knowledge development. Because of the great amount of publications available, only a selection of studies gets cited, for varying reasons. If the selection of citations is associated with study outcome this is called citation bias. We will study determinants of citation in a broader sense, including e.g. study design, journal impact factor or the funding source of the publication. As a case study we assess which factors drive citation in the human literature on phthalates, specifically the metabolite mono(2-ethylhexyl) phthalate (MEHP). A systematic literature search identified all relevant publications on human health effect of MEHP. Data on potential determinants of citation were extracted in duplo. Specialized software was used to create a citation network, including all potential citation pathways. Random effect logistic regression was used to assess whether these determinants influence the likelihood of citation. 112 Publications on MEHP were identified, with 5684 potential citation pathways of which 551 were actual citations. Reporting of a harmful point estimate, journal impact factor, authority of the author, a male corresponding author, research performed in North America and self-citation were positively associated with the likelihood of being cited. In the literature on MEHP, citation is mostly driven by a number of factors that are not related to study outcome. Although the identified determinants do not necessarily give strong indications of bias, it shows selective use of published literature for a variety of reasons

Seventh supplement to the Federated Malay States Government Gazette of Friday, the 7th of December, 1925 (Vol. XVII, No. 24).

No. 779

Systematic Review of observational studies on phthalates

Aim: To conduct a systematic review of epidemiological studies on phthalate exposure, including a request for the study proposal (protocol) and to study determinants of protocol provision. Methods: A literature search was carried out to identify epidemiology studies on phthalate exposure. In addition reference lists and reviews were searched for eligible publications. Corresponding authors were asked to participate in a short telephone interview and to provide a copy of the study proposal (protocol). Study characteristics were scored and their association with protocol provision examined

Review of 2,4-dichlorophenoxyacetic acid (2,4-D) biomonitoring and epidemiology

A qualitative review of the epidemiological literature on the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and health after 2001 is presented. In order to compare the exposure of the general population, bystanders and occupational groups, their urinary levels were also reviewed. In the general population, 2,4-D exposure is at or near the level of detection (LOD). Among individuals with indirect exposure, i.e. bystanders, the urinary 2,4-D levels were also very low except in individuals with opportunity for direct contact with the herbicide. Occupational exposure, where exposure was highest, was positively correlated with behaviors related to the mixing, loading and applying process and use of personal protection. Information from biomonitoring studies increases our understanding of the validity of the exposure estimates used in epidemiology studies. The 2,4-D epidemiology literature after 2001 is broad and includes studies of cancer, reproductive toxicity, genotoxicity, and neurotoxicity. In general, a few publications have reported statistically significant associations. However, most lack precision and the results are not replicated in other independent studies. In the context of biomonitoring, the epidemiology data give no convincing or consistent evidence for any chronic adverse effect of 2,4-D in humans

Impact of changes in human reproduction on the incidence of endocrine-related diseases

The incidence rates of a wide range of diseases and conditions have increased over the last decades. There is controversy over the origin of these increases, whether they are caused by exposure to compounds thought to have an effect on the endocrine system, the \u201cendocrine disruption theory\u201d, or whether some other factor is responsible. In this analysis, the authors take a closer look at the role that changes in reproductive factors have played in this respect. They apply the relative risks of age at first pregnancy and parity or family size to a set of Dutch demographic data from 1955 and 2015 and calculate the percentage of disease increase explained. The decrease in parity over the last decades explains an increase of 26% in testicular cancer. The combination of decrease in parity and increase in maternal age at first pregnancy explains an increase of 34% in hypospadias prevalence. This combination of decreased parity and increased maternal age at pregnancy explains an increase of 24% in childhood obesity prevalence. The authors further point to a perhaps even more profound effect of the trend toward smaller families. This trend has led to an estimated doubling of the proportion of children born from subfertile couples. Since children born from subfertile couples are more likely to be preterm or of low birth weight, the incidence of these conditions must have increased as well. Low birth weight and preterm delivery are risk factors for a wide range of diseases and conditions. The changes in human reproduction over the last decades have had a profound impact on the incidence of a range of diseases and conditions in the next generation and thus provide a sound explanation for a substantial portion of the reported increases.Key messages The incidence rates of a wide range of diseases and conditions have increased in the Western societies over the last decades. Many have argued that these increases are attributable to compounds thought to have effects on the human endocrine system: the endocrine disruption theory This analysis shows, however, that human reproductive factors such as maternal age at first pregnancy and parity explain substantial proportions of the reported increases

Stomach cancer mortality: Geographic comparisons in the Netherlands and in Belgium

The geographic distribution of stomach cancer mortality by province in the Netherlands and Belgium, 1972-1975, is described. Areas of high risk for this disease are identified along the common border of these two countries, suggesting common etiologic factors. © 1982.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

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

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

Scientific citations favor positive results:a systematic review and meta-analysis

Objectives Citation bias concerns the selective citation of scientific articles based on their results. We brought together all available evidence on citation bias across scientific disciplines and quantified its impact. Study Design and Setting An extensive search strategy was applied to the Web of Science Core Collection and Medline, yielding 52 studies in total. We classified these studies on scientific discipline, selection method, and other variables. We also performed random-effects meta-analyses to pool the effect of positive vs. negative results on subsequent citations. Finally, we checked for other determinants of citation as reported in the citation bias literature. Results Evidence for the occurrence of citation bias was most prominent in the biomedical sciences and least in the natural sciences. Articles with statistically significant results were cited 1.6 (95% confidence interval [CI] 1.3-1.8) times more often than articles with nonsignificant results. Articles in which the authors explicitly conclude to have found support for their hypothesis were cited 2.7 (CI 2.0-3.7) times as often. Article results and journal impact factor were associated with citation more often than any other reported determinant. Conclusion Similar to what we already know on publication bias, also citation bias can lead to an overrepresentation of positive results and unfounded beliefs