The closer to the Europe Union headquarters, the higher risk of COVID-19? Cautions regarding ecological studies of COVID-19
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Abstract
Several ecological studies of the coronavirus disease 2019 (COVID-19) have reported correlations between group-level aggregated exposures and COVID-19 outcomes. While some studies might be helpful in generating new hypotheses related to COVID-19, results of such type of studies should be interpreted with cautions. To illustrate how ecological studies and results could be biased, we conducted an ecological study of COVID-19 outcomes and the distance to Brussels using European country-level data. We found that, the distance was negatively correlated with COVID-19 outcomes; every 100 km away from Brussels was associated with approximately 6% to 17% reductions (all P<0.01) in COVID-19 cases and deaths in Europe. Without cautions, such results could be interpreted as the closer to the Europe Union headquarters, the higher risk of COVID-19 in Europe. However, these results are more likely to reflect the differences in the timing of and the responding to the outbreak, etc . between European countries, rather than the ‘effect’ of the distance to Brussels itself. Associations observed at the group level have limitations to reflect individual-level associations – the so-called ecological fallacy. Given the public concern over COVID-19, ecological studies should be conducted and interpreted with great cautions, in case the results would be mistakenly understood.
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SciScore for 10.1101/2020.04.23.20077008: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Ecological bias, or ecological fallacy, is the major limitation of ecological studies in making causal inference. This bias is usually interpreted as the failure of the observed association at the group level to reflect the biological effect at the individual level7. While a strong individual-level effect of an exposure on an outcome …
SciScore for 10.1101/2020.04.23.20077008: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Ecological bias, or ecological fallacy, is the major limitation of ecological studies in making causal inference. This bias is usually interpreted as the failure of the observed association at the group level to reflect the biological effect at the individual level7. While a strong individual-level effect of an exposure on an outcome could result an effect at the group level, i.e., a population with more smokers tend to have more lung cancers compared with a (comparable) population with fewer smokers, the reverse is not always held. One source for ecological bias is that the group-level measures do not necessarily reflect the measures at the individual level, as the latter are not measured at all. Although in our example, the country distance could reflect to some extent the individual-level distance to Brussels of the people living in that country, the COVID-19 epidemic measures were not at the individual level, and there are other factors could bias the association; see below. It is argued that the purpose of some ecological studies is to make inference for the ecological effects of an exposure on group rates, rather than to make inference for the biological effects on individual disease risks8. However, such two purposes tend not to be explicitly differentiated by some studies, and results from studies with ecological purposes are vulnerable to be mistakenly interpreted as biological effects. Furthermore, even with the ecological purpose, cautions are still needed. Ecologi...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
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- No protocol registration statement was detected.
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