Abstract
BackgroundThis study uses bibliometric analysis to describe the state of research about the association of NO2, PM2.5 and noise exposures – three traffic-related pollutants – with cardiometabolic disorders.MethodsWe retrieved references published 1994–2017 from Scopus and classified references with respect to exposure, health outcome and study design using index keywords. Temporal trend, top cited references, used index keywords and the number of hypothesis testing and non-hypothesis testing study design for each group were identified.ResultsResults show PM2.5 is the most frequently studied exposure (47%), followed by both NO2 and PM2.5 exposure (29%). Only 3% of references considered multiple exposures between NO2 and/or PM2.5 and noise, and these were published after 2008. While we observed a growing trend in studies with NO2 and/or PM2.5 and noise and diabetes in the last decade, there is a diminishing trend in studies with noise and diabetes. Different patterns of study designs were found through H/NH ratio, the number of references classified as having a hypothesis (H)-testing design relative to the number of references classified as having a non-hypothesis (NH)-testing design. Studies with NO2 and/or PM2.5 exposure are more likely to have a H-testing design, while those with noise exposure are more likely to have a NH-testing design, such as cross-sectional study design.ConclusionsWe conclude with three themes about research trends. First, the study of simultaneous exposures to multiple pollutants is a current trend, and likely to continue. Second, the association between traffic-related pollutants and diabetes and metabolic symptoms is an area for growth in research. Third, the transition to the use of H-testing study designs to explore associations between noise and cardiometabolic outcomes may be supported by improved understanding of the mechanism of action, and/or improvements to the accuracy and precision of air pollution and noise exposure assessments for environmental health research.
Highlights
This study uses bibliometric analysis to describe the state of research about the association of Nitrogen dioxide (NO2), PM2.5 and noise exposures – three traffic-related pollutants – with cardiometabolic disorders
* Correspondence: rachael.jones@utah.edu 1School of Public Health, University of Illinois at Chicago, Chicago, USA Full list of author information is available at the end of the article on cardiovascular disease and cardiometabolic disorders is an emerging area of research [10,11,12]. While these general trends are known to the environmental health community, this study closely examines trends in research about the association between exposures to PM2.5 [13], NO2 and/or noise with cardiometabolic disorders to gain a better understanding of how research has grown and changed
Though we found the relative frequency of references about multiple exposures (NO2 + PM2.5) and cardiovascular disease have plateaued in the past five years, we expect that research about the impact of the combinations of traffic-related air pollutants (TRAPs) on cardiometabolic disease will increase in the future, due to: continued emphasis on assessing the impact of simultaneous exposures to multiple pollutants [47], interest in other TRAPs like ground level ozone (Fig. 5), improved characterization of particulate matter [48, 49], consideration for TRAPs exposures at locations other than residential address [50, 51], and the increasing use of wearable sensors to measure TRAPs and noise [52,53,54]
Summary
This study uses bibliometric analysis to describe the state of research about the association of NO2, PM2.5 and noise exposures – three traffic-related pollutants – with cardiometabolic disorders. The methodological approach used in this study is bibliometric analysis, which is a quantitative method used to characterize the state of scientific research about a topic through analysis of publications. Bibliometric analysis has been applied in the context of environmental health research, including air quality, typically with a focus on identifying patterns among publications. Wang et al [16] characterized research on the association between particular matter exposure and atherosclerosis and used cluster analysis of Medical Subject Headings (MeSH) to identify eight clusters that he classified into four key topics of research
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