Systematic review of childhood and adolescence sedentary behavior : analysis of the Report Card Brazil 2018

The aim of this study was to summarize studies examining the prevalence of sedentary behavior among Brazilian children and adolescents. A systematic review conducted on eight databases (PubMed, Scopus, Web of Science, LILACS, SPORTDiscus, BIREME, Scielo, and Google Scholar). The criteria applied were: original research; samples including Brazilian children and adolescents; to be a schoolor population-based survey; observational studies using different measures of sedentary behavior; studies showing the prevalence of at least one component of sedentary behavior. Of the 205 studies included, 104 were analyzed. There was a greater concentration of studies in the southern (n=41) and northeastern (n=18) regions. The components more frequently investigated were watching TV (n=36) and screen time (n=32). Only three studies included children under seven years, and the age range more investigated was 10 to 19 years. Most of the studies used a self-reported questionnaire and showed variability in the cut-off point applied (from 2 to 4 hours/day). The prevalence of adolescents who met recommendations ranged from 9.4% to 68.0% for sedentary behavior (<2 hours/day) and from 16.8% to 67.2% for TV viewing (<2 hours/day). The prevalence ranged from 39.1% to 97.7% for computer use and from 47.7% to 98.0% for videogame use. Most of the studies reported that less than half of the adolescents met the recommendations of sedentary behavior and TV viewing. On the other hand, more than half of them devoted less than two hours a day to computer and videogame use.


INTRODUCTION
Sedentary behavior is defined as any human activity that requires an expenditure of less than 1.5 METs to perform 1 and represents most of the activities that constitute the lifestyle of young people 2 .Excessive time in sedentary behavior has been associated with obesity 3 , increased blood pressure 4 , and lower cardiorespiratory fitness 5 .Guidelines have been created in order to reduce negative consequences for health, with recommendation of a maximum time of sedentary behavior of less than two hours to be permitted to children and adolescents, specifically directed at screen activities (e.g., TV viewing, playing videogames, using a computer) 4 .
A study has shown that estimates of sedentary behavior in the young population have increased significantly around the world 6 .Another study involving 5,844 children from twelve countries observed that children spend an average of 8.6 hours in sedentary behavior, and 54.2% of them did not meet the recommendation 6 .According to a Brazilian survey, 60% of elementary school students reported watching TV for more than two hours a day 7 .Data from several European and North American countries have shown that 68% of girls and 66% of boys spend two or more hours a day watching TV 8 .Wide variability in the prevalence and changes of the investigated components was found in the aforementioned studies.
Exploring the prevalence of different components (screen time, TV viewing, sitting time) according to gender may help identify which indicators are more frequent in daily activities among children and adolescents 8 .Studying these questions helps and clarifies future directions of interventions and public policies aimed at reducing sedentary behavior among boys and girls 9 .Thus, the objective of the present investigation was to summarize studies that analyzed the prevalence of sedentary behavior in Brazilian children and adolescents up to 18 years of age.

Measured Outcome
In this review, sedentary behavior was characterized by an energy expenditure ≤1.5 metabolic equivalent, while in a sitting, reclining or lying posture 1 .Self-reported information (e.g.questionnaires about sedentary behavior, TV viewing; videogames and computer use; screen time; and sitting time) and objective measures were included.

Study Search Strategies
A systematic search was performed in the following databases: Medline (PubMed), Scopus, Web of Science (Web of Knowledge), LILACS (Literatura Latino-Americana em Ciências da Saúde), SPORTDiscus, BI-REME (Biblioteca Regional de Medicina), Scielo, and Google Scholar in February 2018.The search strategy included four groups of descriptors (see Supplementary file 1).The Boolean operator "AND" was used for combinations among descriptor groups.The truncation symbols ($, * or "") specific for each database were also used to increase the range of searches for the descriptor variations.Searches were conducted with the descriptors in English and Portuguese.The searches of the electronic databases were supplemented with a screening of the reference list of retrieved articles in order to find potentially relevant titles.

Selection process
The initial selection was based on the titles of manuscripts, and when there was uncertainty, on the abstract.After this step, articles were obtained in the full text version and subsequently analyzed according to established selection criteria, and the reference lists of the articles were evaluated.All of these steps were performed independently and conducted by two pairs of reviewers (PCS/AC and AB/LM), and a third pair of senior reviewers (KS/VB) helped when there were disagreements.

Selection criteria
To be eligible for inclusion in this systematic review, studies needed to be: (I) original research published in peer-reviewed journals (dissertations and monographs were not included because it was impractical to systematically search them); (II) samples including Brazilian children and adolescents aged 0-18 years (or a mean age within this range) or a sample comprising other age years (when data had been presented separately); (III) to be a school-or population-based survey with information about the methodological procedures of representation of the target population (e.g., random sampling); (IV) observational studies using different methods for sedentary behavior assessment (e.g., self-report, structured interviews, objectively measured sedentary behavior, and steps per day); and (V) studies showing the prevalence of at least one component of sedentary behavior (e.g., TV viewing, use of computer and videogames, and time in the sitting position).

Data extraction and Analysis
Data extraction was performed by four authors (PCS/AC and AB/LM), half of the references were read by each pair, and a third author (KS or VB) helped when the article did not report the information clearly.The prevalence of sedentary behavior was extracted always in a positive way according to the established cut-off point of each article.For instance, if the article established a cut-off point >2 hours/day of TV viewing, we extracted the prevalence of those who spent less than 2 hours in this behavior.In addition, articles from the same study were coupled in order to avoid duplication of information.Therefore, information from the same study but in different articles, such as cut-off point and strata, was reported in the review, making it clear that they were different articles from the same investigation.
The prevalence of meeting the sedentary behavior recommendations is presented for the sample as a whole and according to gender.The included articles were organized into tables according to the criteria used to identify the prevalence of sedentary behavior in alphabetical order considering the location of the studies.Additionally, data of its components (watching TV, videogame and computer use) were presented.

RESULTS
The results are summarized in the flowchart in Figure 1.The initial search of eight databases located 1,490 potential articles.After removal of duplicate articles 1096 records remained.Next, titles and abstracts were read, 171 full papers were selected for further review, and 9 other studies were located in the reference lists of these articles.After reviewing the full content of the articles, 76 were excluded (see supplementary material 2) and 104 met the inclusion criteria.
The 104 original studies included were published from 2004 10 to 2018 11,12 and an interval from 2001 to 2015 was observed for the year of data collection.When different articles were found to report results about the same investigation, the articles were grouped, for a total of 81 studies.There was a greater concentration of studies in the southern (n= 41) and northeastern (n= 18) regions, while few studies were carried out in the southeast (n= 12), north (n= 4), or central-west (n= 3), or involved a national scope (n= 3).
Regarding the components of sedentary behavior investigated, TV viewing (n= 36) and screen time (n= 32) were those more investigated in the articles included, followed by computer (n= 22) and videogame (n= 7) use.Few studies 11,[13][14][15][16][17] investigated other components of sedentary behavior such as indicators that did not involve screen time.
For TV time, the range for adolescents who met the recommendations was 16.8% 69 to 67.2% 65 .For this component, most of the studies also reported a prevalence below 50% of subjects meeting the recommendation.Among girls, all studies showed a prevalence of less than 50% of adolescents who met the recommendation (prevalence range: 20.5% 80 to 58.4% 68 ) while for boys, three studies reported a prevalence higher than 50% (prevalence range: 20.5% 71,80 to 56.3% 10 ) (Table 2).

DISCUSSION
This systematic review included data from 105 studies involving representative samples of Brazilian children and adolescents.Most of the studies showed that less than half the participants met the recommendations of total screen and TV time; however, more than half the participants met the recommendations regarding computer or videogame use.Thus, the findings revealed: i) a higher concentration of studies in the southern and northeastern regions of Brazil; ii) few studies with children less than seven years of age; iii) the components more investigated were TV time and screen time; iv) there was higher methodological variability of the components assessed, measurement tools and cut-off points used to examine the sedentary behavior.
In the last ten years, the number of publications on this subject has increased and consequently also their quality, based on sophisticated instruments and statistical analyses 11,16 .This scenario has also been observed in Brazil 117,118 .The first Brazilian studies on sedentary behavior focused on TV viewing time 10,95 , followed by studies analyzing other screen components such as computer 87 , videogames 12 , and sitting time 13 .Moreover, a considerable imbalance of published data was observed among the various Brazilian regions.Ramires et al. 118 suggested the need to implement research centers in the Center-West and North regions of the country with the objective of guaranteeing the dissemination of knowledge.
In the present review, there was wide variation in the proportion of young people who complied with the recommendation of less than two hours daily among studies (screen time: 9.4% to 68.0%; TV: 16.8% to 67.2%; computer: 39.1% to 97.7%; videogame: 47.7% to 98%).Part of this fluctuation can be explained by the use of different questionnaires (some of them not validated), as reported in a previous study 119 .Other methodological aspects have also been reported in another review 117 , including the variability among the components of sedentary behavior investigated and the cut-off points (e.g.≤ 2 hours, 3 hours and ≤ 4 hours) used.These differences impair the examination of the trend of sedentary behavior over the years; as well as the comparison of estimated prevalence.
Specifically for screen time and TV, most of the studies that used a cut-off point of ≤ 2 hours a day (screen time: 17 of 20 studies; TV: 15 of 19) reported that less than half the boys and girls met the recommendations.Regarding screen time, the sum of the use of electronic devices may contribute to the failure to comply with recommendations.Perhaps the cut-off point for screen time should be different, considering that we have grouped a total time of use into screen activities.In contrast to computers and videogames, most Brazilian households have access to television, which may explain the lower variability in the proportion of TV viewing among studies 120 .
In contrast, for computer and videogames, studies with a cut-off point of ≤ 2 hours a day (computer: 9 of 11 studies, videogame: 3 of 4) reported that more than 60% of adolescents comply with the recommendation.Despite the growing use of computers and videogames by adolescents 116 , these electronic devices are not yet accessible to most Brazilian households 120 .Another aspect that can contribute to the greater variability of these components in Brazilian data might be social and income inequality 43,116,121 .
Considering the use of computer for boys and girls, five out of eight studies reported that more than half the boys met the recommendation, whereas for girls seven out of eight studies reported that more than half met the recommendation.For videogames, two out of three studies reported that more than half the boys complied with the recommendation, and for girls all studies (three) reported this result.Regarding computers, other studies also showed that boys spend more time using computers than girls 63,122 , mostly with games 122 .Girls spent more time on social networking sites, listening to music, and online reading 123 Several factors can influence these differences between genders, such as the lack of social interaction and the violence present in the context of games, which may be related to less use by girls 124 .
Several limitations of this review are difficulty in comparing studies due to the high heterogeneity of the components of sedentary behavior investigated, the instruments and cut-off points used (problems that could be avoided with the inclusion of more delimited criteria); absence of assessment of risk bias, and the choice to analyze only studies that used a cut-off point of less two hours (current recommendations), although all other studies were described in the tables.In summary, less than half the children and adolescents met the recommendations of screen time and TV viewing, and most of them followed the recommendations regarding time spent using the computer or videogames.Only computer use differed between genders, with boys meeting recommendations less than girls.
We suggest that studies be conducted in the northern and centralwestern regions of Brazil to determine the reality of these populations, as well as studies with preschool children.In addition, we recommend standardizing and validating questionnaires and the use of cut-off points according to international guidelines.New components of sedentary behavior could also be investigated such as cell phones and tablets, as well as the type of subject consumed or activity chosen during the time in front of the screens.Finally, attention is drawn to the high prevalence of young people who do not meet the recommended use of screen time, and even exceed this time in a single component.SB: Sedentary Behavior.The Boolean operator "AND" was used for combinations among descriptor groups.The truncation symbols ($, * or "") specific to each database were also used to increase the range of searches for the descriptor variations.Searches were conducted with the descriptors in English and Portuguese, when required.The search of the electronic databases was supplemented by a screening of the reference list of retrieved articles in order to find potentially relevant titles and the personal library.

Figure 1 .
Figure 1.Flowchart of the studies through the phases of the systematic review.

Table 2 .
Description of the prevalence of sedentary behaviors among Brazilian children and adolescents.
Text Word] OR sedentarism [Text Word] OR inactivity [Text Word] OR sedentary behavio* [Text Word] OR sedentary lifestyle [Text Word] OR computer use [Text Word] OR screen view* [Text Word] OR sitting time [Text Word] OR computer game [Text Word] OR video game [Text Word] OR television watch* [Text Word] OR TV watch* [Text Word] OR TV view* [Text Word] OR screen time [Text Word] OR smartphone [Text Word] OR smart phone [Text Word] OR mobile phone [Text Word] OR small screen* [Text Word] OR ("screen based entertainment") OR ("screen-based entertainment")) Text Word] OR teenage [Text Word] OR adolescent [MeSH Terms] OR adolescent [Text Word] OR adolescence [Text Word] OR students [MeSH Terms] OR student [Text Word] OR child [Text Word] OR children [Text Word] OR "young people" [Text Word]) Instrument (self-report OR checklist OR recall OR 24h OR interviews OR questionnaire OR diary OR assessment OR survey OR measurement OR Acceleromet* OR pedomet OR inclinomet OR ((objectiv* measur*) OR (direct* measure*))) AND (Brazil* OR Brazilian)