The impact of physical activity to the child’s quality of life: a bibliometric study

Background: The application of bibliometrics in healthcare research is becoming popular, however at present it is still an under-researched area. Methods: In our study we used a bibliometric technique called bibliometric mapping to visualize the published research regarding the influence of physical activity to children’s quality of life. The research was visualized in the form of both chronological and cluster science landscapes. Science landscapes, contrary to conventional reviews, capture the relationships between multiple topics and concepts, enabling the generation of “synthetic reviews”. Results: Evolutionarily, three distinct research phases appeared, namely research on influence of physical activity on various chronic non-communicable diseases; research on quality of life and childhood diseases related to physical activity; and outcome-related research. The research consists of six main topics: asthmatic child and exercising, blood diseases, health-related quality of life, obesity and chronic diseases, childhood obesity and behaviour, and depression and health outcomes. Conclusions: The study identified some research that may be helpful to general paediatricians whose everyday practice or research is not focused on physical activity and child’s quality of life, but wants to learn about the taxonomy of the topics, the most interesting discoveries, guidelines and practices and the state of the art in the field. It also revealed some hidden association, otherwise not easily identified, even by informed researchers and clinicians.


Introduction
The role of bibliometrics in healthcare research has been excellently described by Lewison and Devey 1 : "Bibliometrics is to scientific papers as epidemiology is to patients." Indeed, in 1990 bibliometrics first became a medical subject heading. Consequently, the application of bibliometrics by health professionals to analytical, clinical, informational and academic areas of interest is becoming more extensive; however, at present it is an unexploited area of a fruitful research 2 .
Interdisciplinary research concerning the influence of physical activity and sport on children's quality of life is increasingly becoming more and more important. In their review paper Buttitta et al. 3 reported that several factors are associated with children's quality of life; among them physical activity is one of the most important, especially in in those with pre-existing diseases. Various malignant diseases and anticancer therapy in children both drastically affect daily life activities, including high-performance sports. However, both random and non-random feasibility studies show positive effects of physical activity on clinical and psychosocial outcomes. Consequently, every effort should be made to maintain physical activity during paediatric cancer therapy 4 . Comparable findings for congenital heart diseases, were reported by Dulfer et al. 5 .
Since our research area interest is multidisciplinary, we had an opportunity to employ a bibliometric technique called bibliometric mapping. Bibliometric mapping visualizes academic research in the form of scientific landscapes 6 . Science landscapes, contrary to conventional reviews, which focus on particular research questions, extract information at various levels and capture the relationship between multiple topics and concepts, creating "synthetic reviews". Scientific landscapes are still relatively rarely used; however, those published have been well received by the scientific community 7 .

Methods
Bibliometrics could be defined as the application of mathematical, statistical and heuristic methods to scientific publications 8 . Bibliometric mapping is a recent addition to techniques already used in bibliometrics in medicine 2 . Bibliometric mapping aims to visualize different facets of literature production based on different co-occurrences (i.e. words, authors, organisations, journals) 9 , co-citations 10 and bibliographical coupling 11 . Bibliometric mapping can be automated using various software tools. Among open licence software tools, VOSviewer 12 is very versatile and easy to use 13 . Both bibliometric mapping and VOSViewer have been successfully used in health related fields 14 .

Bibliographical dataset and corpus
The corpus was extracted from the Scopus bibliographical dataset, because of Scopus broad coverage of various journals, book chapters and conference proceedings on one hand and on the other hand because of Scopus' extensive and easy to use search and analytical functions. The search was made on 12th January 2019 using the search keyword string child* AND ("physical activity" or "sport") AND "quality of life" in information source titles, abstracts and keywords for the whole period covered by Scopus.

Data extraction and analysis
Publication year, source title and author's country of affiliation were extracted by Scopus services. Abstracts were exported as comma separated values (CSV) files to enable further analysis by the VOSviewer (V1.6.9) and Excel software (Version 2016). Cluster and chronological scientific landscapes were generated for all terms with an occurrence frequency larger than 30. Common words such as report, significance, trial, study and baseline were ignored using a customised thesaurus file (see Underlying data 15 ). Similarly, synonyms like body mass index and BMI were integrated into one term. The Attraction was set to 4, Min. Cluster size to 8, Resolution to 1.25; all other VOSViewer parameters were set to default values.

Meta-synthesis
The popularity of a term (size of the term font and associated square) and relatedness between terms (terms located near each other are more related than those further apart) in both cluster and chronological scientific landscapes were analysed using meta-synthesis 16 . An appropriate topic was determined for each cluster based on the analysis of most popular terms belonging to the cluster.

Results
The search resulted in 2334 publications (1637 articles, 419 reviews, 66 conference papers, 50 editorials, 35 notes, 29 book chapters, 19 letters, 19 short communications and 24 other types of publications; see Underlying data 15 ). The most popular journals in which the above publications appeared are shown in Table 1. The most prolific journal was BMC Public Health with 31 publications. The highest ranked journal in the selected field was Pediatrics, with 21 publications (621 st place according to SCImago Journal Rank -SJR, which ranks within the top 2% of all source titles indexed by SciMago. Interestingly, all of the most prolific source titles are ranked in the top quarter of all journals. Their contribution to the total literature production on our topic of interest accounts for 12.4%. As expected most of the most prolific source titles are from the field of paediatrics, others relate to quality of life or from general areas. Surprisingly no source titles related to sport or physical activity were ranked among the most prolific source titles -the first (American Journal of Sports Medicine) is in 15 th place with 11 publications.
The most productive countries are presented in Table 2. All of them have advanced heath, industrial and economic systems, high BDP and are also leading countries in research and development.
The top 10 countries produced more than 83% of all publications, indicating that literature production is regionally centred.  According to the figure the research development went through three main phases, namely: The cluster science landscape (Figure 3) consists of six clusters. Meta-synthesis revealed six topics, as shown in Table 3.

Discussion
It is interesting to note some details evident from the derived topics above and associations between terms: • The quantity of research concerning physical activity in relation to asthma, but not only as a single disease, but also in combination with obesity and diabetes. Di Genova et al. 18 claim that growing evidence shows the existence of an "obese asthma" phenotype characterised by difficult-to-manage asthma. Additionally, Atay and Berket 19 show that obesity results in various co-morbidities in children and adolescent.
• The increasing incidence of psychosomatic diseases and the beneficial effects of physical activity. Hrafnkelsdottir et al. 20 reports that less screen time and more intense physical activity lowers the risk of mental health problems.
• The broadness of the spectrum of diseases related to child's quality of life and physical activity. Studies highlighted that children with overweight/obesity and related co-morbidities and lifestyle behavioural risk factors, had significantly lower healthy-related quality of life 21,22 .

Conclusion
Using bibliometric mapping we created two scientific landscapes on the topic of research, the influence of physical activity to children's quality of life. To the best of our knowledge, this is the first such attempt in the paediatric field. We identified six distinct topics and also visualised the chronological aspect of the research literature production. The study revealed some knowledge that might be helpful to an "outsider" who wants to learn about the taxonomy of the topics, the most interesting discoveries, guidelines and practices and the state of the art in the field. It can also help the "seasoned insiders" better understand more specialised research including that is out of their immediate scope of interest. Additionally, it can reveal hidden facts, not easily identified, even by informed researchers and clinicians.

Grant information
The author(s) declared that no grants were involved in supporting this work.
11. Biscaro C, Giupponi C: Co-authorship and bibliographic coupling network 1. The work is interesting for readers and should be indexed. The following should be done first:

Open Peer Review
In the discussion, explain briefly the possible relationships between illness and physical activity. Namely, it is important to note what are the mechanisms of how physical activity can affect disease, but also vice versa, in a wide range of conditions, from asthma to air pollution.
In discussion, avoid overlapping conditions (asthma and obesity).

If applicable, is the statistical analysis and its interpretation appropriate? Yes
Are all the source data underlying the results available to ensure full reproducibility? Yes The manuscript develop a science mapping analysis of the physical activity on children and the effect in their quality of life. To do that, VOSViewer software tool is employed.
In general, the paper is well organised and written. Moreover, the software tool is appropriate for this analysis and authors use it properly.
In what follows, some comments and suggestions are listed: I miss some references to the origins of co-word analysis, science mapping, or generally, science of science. Authors focus too much on bibliometrics on health, but there are important references out of this field. Moreover, authors should cite some recent bibliometric studies developed in health, for example in cancer, rehabilitations, etc.
The reference to VOSViewer is incorrect. Author should cite the paper where the software is presented. Figure 2 is confusing. Authors should provide other kind of visualisation. Also, authors should describe better the conceptual evolution of this research field. Discussion should be better described. At this moments it is just a sequence of itemises. Author should provided a clear speech.
Conclusions are just a summary of the paper.

Is the work clearly and accurately presented and does it cite the current literature? No
Is the study design appropriate and is the work technically sound? Yes

Are sufficient details of methods and analysis provided to allow replication by others? Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Yes Are the conclusions drawn adequately supported by the results? Yes No competing interests were disclosed.