Discussion
LSR, as a new method of SR updating, aims to break down the trade-off between rigour and currency of current methods and provide a reliable and up-to-date synthesis of evidence.49 This study reviewed 213 existing LSR-related studies and found that studies conducted based on LSR methodology have overgrown since 2020, and LSR was gradually gaining more attention and recognition by more researchers. The development level of LSR varied greatly among different countries, with Europe, North America and Australia leading the way. COVID-19-related research will continue to be the main focus of LSR for a long time. More than half of the LSR-based series has not yet been updated, and more practice details need to be standardised.
Seven years have passed since Elliott et al first proposed the LSR concept.6 The previous studies on LSR were tepid, but the outbreak of COVID-19 also triggered many related studies. However, in general, research on LSR was still relatively scarce, and the field was still in its early stages of development, with much room for growth. Throughout the development of LSR, we could find that the integration of living evidence has been expanded and applied in a short period, including the release of the LSR systematic methodology, the proposal of the LNMA framework and the development of living guidelines. After a certain period of exploration, the methodology associated with LSR has been refined through experimentation. The rapid global epidemic of COVID-19 has prompted numerous clinical trials, which raised high demands for the rapid and efficient integration of clinical evidence,50 51 essentially promoting the development of LSR-related studies and, to some extent, demonstrating the potential for LSR development.
The vast majority of published studies were in English (97.7%). As a relatively new concept, LSR has not been widely concerned by researchers. Some institutions and scholars from Italy and Germany had certain advantages in this field and dominated the research component. There was a relatively close collaboration between them, but collaboration between different groups was relatively sparse. We look forward to further collaboration to promote the development of LSR-related research. LSR research has been conducted worldwide, but some differences and imbalances remain. LSR has been studied more frequently in Europe, North America and Australia, and a great deal of cooperation was carried out with other countries. As more and more scholars worldwide gradually realise the feasibility and significance of LSR, it is bound to progress and develop even more soon. Although the concept of LSR was relatively new, its related research was still widely accepted. Most journals that published LSR research were included in SCI journals. Many flagship journals such as BMJ, Ann Intern Med, J Clin Oncol, Eur Urol, etc, have shown high acceptance.
There were few existing studies on LSR, with a relative concentration of research hotspots. The main focus was methodology development and exploration, child growth and nutrition, disease epidemiology, diagnosis treatment and prognosis, and the prevalence, treatment and prognosis of COVID-19. In the short time since the concept of LSR was introduced, scholars have been exploring which types of diseases could be substantively helped by the LSR methodology. Since the outbreak of COVID-19 in late 2019, there has been an explosion in the use of the LSR methodology. LSR could provide rapid and compelling evidence for public health outbreaks, contributing partly to disease treatment and infection control. In the global COVID-19 pandemic, the rapid integration and updating of evidence provided by LSR have contributed significantly to the pandemic’s prevention, treatment, control and prognosis, as evidenced by the high citation rate of the LSR series of studies. As a result, the LSR methodology has received increasing attention and will be applied in more innovative ways in the future. On the other hand, the feasibility and necessity of the LSR methodology have been proven by various empirical studies, which further contributed to the refinement and rigour of the LSR methodology and provided help and reference for future research and application in more areas.
According to ICD-11, current hotspots were mainly focused on certain infectious or parasitic diseases. Many previous studies and topics based on LSR methodology were updated irregularly but have been overshadowed by the strong impact of COVID-19. Methodological exploration of LSR also occupied a large area of existing research, with scholars committed to the ongoing promotion of its application and continuous improvement of the shortcomings of LSR methodology and further standardised differences in practice.
Although Elliott et al’s system introduction to the LSR concept described its production schedule,5 it stated that the LSR needed pre-registration and updated roughly once a month. Based on the findings, fewer than half of the current studies have been updated at least once, and many of these did not complete standardised registration or changed their plans midway through the process. Most of the registered research was not reported and updated according to their protocols, and there was no set frequency of updates. Different LSR studies were updated in various forms, such as Article, Review and Letter, and no uniform form has been reached.
Considering the distribution of thematic trends and the current state of the global epidemic, COVID-19 and its virological studies, patient recovery and prognosis will remain a hot topic for LSR research for a long time to come. Although the CENTER-TBI project was launched in 201518 and has been committed to improving the medical care treatment and treatment difference of TBI patients, the thematic outbreak only appeared in 2021 because the coverage renewal strategy of the project replaced previous studies. The update strategy varied considerably between studies. Not all studies retained all the evidence updated in previous dynasties, and some LSRs retain only the evidence of the latest issue, which was also worth our attention. The LNMA and living guidelines have attracted much attention in recent years. We look forward to their further application and dissemination, thus contributing to the continuous progress of EBM.
After carefully reviewing existing studies on LSR, we also raised specific considerations. Since LSR is a process of continuous dynamic renewal and its workload is often substantial, most LSR studies did not mention plans to end or discontinue research. Some studies also failed to explain the advantages of LSR over cumulative MA or whether there is a need for conversion between the two, which may be instructive for further clinical trials. Some LSR studies maintained the same title and coauthor order in historical updates, which may lead readers to believe they were mistakenly the same study. This indicates that LSR studies need to standardise their replacement evolution while maintaining series’ similarity to help distinguish them. As clinical studies are usually undertaken freely, and LSRs are often conducted with a clear purpose, it is difficult to track the differential outcome indicators included in each study, which inevitably leads to a loss or waste of resources in the original study. In traditional SR and MA, the evidence quality is usually assessed using the GRADE Working Group method.52 As for the specificity of the evidence integration of LSR, we also need to determine the quality of its update. However, we are not sure whether the GRADE system is entirely appropriate. In addition, we also mentioned above the issue of the updated presentation form, and we look forward to the refinement and progress of this excellent research method in practical experiments.
To our knowledge, this is the first study to provide a comprehensive bibliometric analysis of the development of the LSR since it was proposed, the current state of LSR-related research, and future perspectives. Based on the comprehensive review and visual presentation, we also put forward some reflections on the research using this methodology. However, there are still some potential limitations in our study. First of all, although we searched the LSR-related studies as comprehensively as possible and made manual supplements, we could still not obtain old versions of a small number of coverage update studies, which might cause differences in literature count, but would not affect our assessment of update frequency. Second, in the author analysis, we tried our best to find the affiliation of similar authors. If they were from the same unit, we added up their contributions. However, we could not tell whether several authors of the same name automatically merged by the software were the same researcher.