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.
Preference for sons and smaller families and, in the case of China, a one-child policy, have contributed to missing girl births in India and China over the last few decades due to sex-selective abortions. Selective abortion occurs also among Indian and Chinese diaspora, but their variability and trends over time are unknown. We examined conditional sex ratio (CSR) of girl births per 1000 boy births among second or third births following earlier daughters or sons in India, China, and their diaspora in Australia, Canada, United Kingdom (UK), and United States (US) drawing upon 18.4 million birth records from census and nationally representative surveys from 1999 to 2019. Among Indian women, the CSR in 2016 for second births following a first daughter favoured boys in India (866), similar to those in diaspora in Australia (888) and Canada (882). For third births following two earlier daughters in 2016, CSRs favoured sons in Canada (520) and Australia (653) even more than in India (769). Among women in China outside the one-child restriction, CSRs in 2015 for second order births somewhat favoured more girls after a first son (1154) but more heavily favoured boys after a first daughter (561). Third-birth CSRs generally fell over time among diaspora, except among Chinese diaspora in the UK and US. In the UK, third-birth CSRs fell among Indian but not among other South Asian diasporas. Selective abortion of girls is notable among Indian diaspora, particularly at higher-order births.
The effect of calcium supplementation on bone mineral accretion in people under 35 years old is inconclusive. To comprehensively summarize the evidence for the effect of calcium supplementation on bone mineral accretion in young populations (≤35 years).
This is a systematic review and meta-analysis. The Pubmed, Embase, ProQuest, CENTRAL, WHO Global Index Medicus, Clinical Trials.gov, WHO ICTRP, China National Knowledge Infrastructure (CNKI), and Wanfang Data databases were systematically searched from database inception to April 25, 2021. Randomized clinical trials assessing the effects of calcium supplementation on bone mineral density (BMD) or bone mineral content (BMC) in people under 35 years old.
This systematic review and meta-analysis identified 43 studies involving 7,382 subjects. Moderate certainty of evidence showed that calcium supplementation was associated with the accretion of BMD and BMC, especially on femoral neck (standardized mean difference [SMD] 0.627, 95% confidence interval [CI] 0.338–0.915; SMD 0.364, 95% CI 0.134–0.595; respectively) and total body (SMD 0.330, 95% CI 0.163–0.496; SMD 0.149, 95% CI 0.006–0.291), also with a slight improvement effect on lumbar spine BMC (SMD 0.163, 95% CI 0.008–0.317), no effects on total hip BMD and BMC and lumbar spine BMD were observed. Very interestingly, subgroup analyses suggested that the improvement of bone at femoral neck was more pronounced in the peripeak bone mass (PBM) population (20–35 years) than the pre-PBM population (<20 years).
Our findings provided novel insights and evidence in calcium supplementation, which showed that calcium supplementation significantly improves bone mass, implying that preventive calcium supplementation before or around achieving PBM may be a shift in the window of intervention for osteoporosis.
This work was supported by Wenzhou Medical University grant .