Earlier this year an editorial explained what eLife editors look for in a paper: ‘For us, the ideal eLife paper presents an accurate description of data that makes others in the field think differently and moves the field forward’ (Malhotra and Marder, 2015). Here we outline how this applies to papers in epidemiology and global health.
First, as with all manuscripts submitted to eLife, we ask if the submission addresses an important question and uses study designs that provide a reasonably clear answer to that question. The disciplines of epidemiology and global health sit squarely on the boundary between the natural, clinical and social sciences, so a range of study designs can be used. Experimental, observational and theoretical lines of enquiry may all be appropriate; both qualitative and quantitative methods may also be used. Health and disease are determined by a host of physical, biological, psychological, technological, social, economic and political factors, and these factors need to be investigated both individually and in combination. So eLife has no pre-conceived notions of what constitutes a good epidemiology or global health paper; certainly we do not limit ourselves to experimental studies or studies rooted in the natural sciences alone. Indeed, we welcome the best papers across the entire gamut of disciplines that contribute to these fields, including those that use rigorous scientific methods to explore the impact of behavioural and socioeconomic factors on health.
Second, research in epidemiology and global health often directly informs decisions at the hospital bedside or at the planning office. Like the editors who handle submissions in other areas of the life and biomedical sciences, we seek submissions that represent the best quality science in terms of rigor and insight. However, researchers in epidemiology and global health have an additional responsibility to maximise the potential of their work to save lives and improve health. Hence we privilege submissions that have the greatest potential impact on health around the world, especially the health of the worst off. This might be an analysis that could lead to a new approach for cancer care or malaria prevention that could save millions of lives, or it could be the discovery of a risk factor for an orphan disease which we previously had little hope of preventing or curing. This does not exclude methodological papers that may not immediately save lives but are highly likely to enable later studies that do. We also welcome papers that are so clear and persuasive in the way they express important truths that they will be read and re-read by clinicians and policy-makers. And since eLife is an open access journal, all articles are freely available to everyone.
Third, we recognise that excellent science can look different in epidemiology and global health because studies are often less precise and controllable than in many of the biological sciences, let alone the physical sciences. Preliminary findings often need to be corroborated with larger, better controlled studies and, eventually, the syntheses of many pieces of relevant evidence. Hence we welcome reports of high-quality clinical trials, along with major reviews and meta-analyses that provide the strength of evidence that will finally allow the findings of smaller studies to be translated into life-saving decisions. Ultimately, we ask ourselves: does this manuscript constitute a substantial step towards a clear answer to an important global health question?
Ultimately, we ask ourselves: does this manuscript constitute a substantial step towards a clear answer to an important global health question?
Much in epidemiology is of corroborative value. Given the bluntness of our toolbox, epidemiological findings must be replicated before they can be considered as evidence for the need to change practice in medicine and public health. We respect that but believe that papers that attempt to corroborate previous findings without taking a substantial step forward, or bringing a new angle to the problem, will have a better home in specialty journals. We seek to reward innovative and smart explorations of population health data. Sometimes the intellectual excitement that a paper elicits does not come from the sophistication of the methodology but from the clever use of simple methods to reveal a possibly causal association that was hidden from view in previous investigations. Eureka moments exist in epidemiology; we wish to display them prominently in eLife.
We recognise and celebrate the fact that global health is now a truly international endeavour, and we are especially keen to receive submissions from the low- and middle-income nations that are under-represented in most journals, including eLife. In the same vein, we think it stands to reason that papers using new data collected in these countries should normally include co-authors from the countries whose health-related data are the focus of the investigation. How else could these studies have captured the appropriate context for an in-depth exploration of the research problem?
In conclusion, when making decisions about submissions in epidemiology and global health, we look for all the things you would expect to see in papers in a good journal—such as a clear question, clever insights and clear clarity of logic—combined with results and findings that have the potential to improve human health.
Few studies have assessed the role of individual plasma cholesterol levels in the association between egg consumption and the risk of cardiovascular diseases. This research aims to simultaneously explore the associations of self-reported egg consumption with plasma metabolic markers and these markers with the risk of cardiovascular disease (CVD).
Totally 4778 participants (3401 CVD cases subdivided into subtypes and 1377 controls) aged 30–79 were selected based on the China Kadoorie Biobank. Targeted nuclear magnetic resonance was used to quantify 225 metabolites in baseline plasma samples. Linear regression was conducted to assess associations between self-reported egg consumption and metabolic markers, which were further compared with associations between metabolic markers and CVD risk.
Egg consumption was associated with 24 out of 225 markers, including positive associations for apolipoprotein A1, acetate, mean HDL diameter, and lipid profiles of very large and large HDL, and inverse associations for total cholesterol and cholesterol esters in small VLDL. Among these 24 markers, 14 were associated with CVD risk. In general, the associations of egg consumption with metabolic markers and of these markers with CVD risk showed opposite patterns.
In the Chinese population, egg consumption is associated with several metabolic markers, which may partially explain the protective effect of moderate egg consumption on CVD.
This work was supported by the National Natural Science Foundation of China (81973125, 81941018, 91846303, 91843302). The CKB baseline survey and the first re-survey were supported by a grant from the Kadoorie Charitable Foundation in Hong Kong. The long-term follow-up is supported by grants (2016YFC0900500, 2016YFC0900501, 2016YFC0900504, 2016YFC1303904) from the National Key R&D Program of China, National Natural Science Foundation of China (81390540, 81390541, 81390544), and Chinese Ministry of Science and Technology (2011BAI09B01). The funders had no role in the study design, data collection, data analysis and interpretation, writing of the report, or the decision to submit the article for publication.
The endocannabinoid system consists mainly of 2-arachidonoylglycerol and anandamide, as well as cannabinoid receptor type 1 (CB1) and type 2 (CB2). Based on previous studies, we hypothesized that a circulating peptide previously identified as Osteogenic Growth Peptide (OGP) maintains a bone-protective CB2 tone. We tested OGP activity in mouse models and cells, and in human osteoblasts. We show that the OGP effects on osteoblast proliferation, osteoclastogenesis, and macrophage inflammation in vitro, as well as rescue of ovariectomy-induced bone loss and prevention of ear edema in vivo are all abrogated by genetic or pharmacological ablation of CB2. We also demonstrate that OGP binds at CB2 and may act as both an agonist and positive allosteric modulator in the presence of other lipophilic agonists. In premenopausal women, OGP circulating levels significantly decline with age. In adult mice, exogenous administration of OGP completely prevented age-related bone loss. Our findings suggest that OGP attenuates age-related bone loss by maintaining a skeletal CB2 tone. Importantly, they also indicate the occurrence of an endogenous peptide that signals via CB2 receptor in health and disease.