INTRODUCTION

Sedentary behavior refers to a set of activities performed with the body in a sitting or reclining position and with energy expenditure close to resting values ​​(<1.5 MET) ¹ . International recommendations recommend that children and adolescents should limit to two hours per day, at most, the time dedicated to sedentary behaviors such as watching television, using the computer, playing video games, talking to friends or similar ² .

Sedentary behavior is recognized as a public health issue ³ and is related to harmful effects on health ⁴ . Studies have shown that exposure to sedentary behavior (SBE), in addition to being associated with obesity ⁵ , metabolic syndrome ⁶ , diabetes mellitus ⁷ and cardiovascular diseases ^{4,8 ,} can be a risk factor for mortality regardless of the level of physical activity of the individual ⁹ . A national survey showed that 59.8% of adolescents were exposed to at least two hours of television per ^{day 10} .

In this context, it appears that, despite the recognition of the importance of low ECS as a factor in health promotion and disease prevention, many adolescents fail to achieve the ECS levels recommended by international institutions ¹¹ . Furthermore, studies show that young people tend to extend this behavior into adulthood ¹² .

Therefore, this study is justified by the need to identify the level of physical activity and ECS and associated factors in adolescents. Demographic and socioeconomic characteristics may justify the possibility of different outcomes among Brazilian states and support the development of public policies to promote health for the adoption of healthy lifestyles among adolescents in the state of Sergipe, Brazil.

Thus, this study aimed to verify the prevalence of ECS and analyze its association with indicators of demographic and socioeconomic conditions in adolescents in the state of Sergipe in the years 2011 and 2016.

METHODS

Epidemiological studies of secular trends, with a cross-sectional design, were carried out in high school students from the state education system, residing in the state of Sergipe, Brazil. To this end, two surveys entitled “Secular trends on health risk behaviors in adolescents: CRiS_Adolescents Study” were conducted, developed by the Physical Education and Health Research Group of the Federal Institute of Education, Science and Technology of Sergipe (GPEFiS/IFS).

The population consisted of students aged 14 to 19 years of both sexes, regularly enrolled in the State High School System, in the daytime and evening shifts. The Stat-Calc program available in the Epi Info software

was used to calculate the sample size of the research. To estimate the sample size in the prevalence analysis, the population size was considered, the estimated prevalence of 50% as the highest expected, the confidence interval of 95% and a tolerable sampling error of 5% were considered. For the association analysis, in addition to the information described above, a statistical power of 80% and an Odds Ratio (OR) of 1.2 were considered. In order not to lose sample representativeness, 20% of students were added due to various reasons, such as: participant refusal, age greater or less than that established in this study, not answering important questions such as gender and age.

Stratified sampling was used in two stages: (1) stratified sampling process proportional to the size of the region, according to the size of the educational unit (1 = up to 199 students; 2 = 200-499 students; 3 = 500 students or more). Thus, considering the size of the schools, the random selection criterion was established to select 25% of the state educational units (155 educational units), totaling 39 (2011) and 42 (2016) schools; (2) the classes were selected proportionally according to the school grade and shift, through the simple random process, considering 20 students per class. The final sample consisted of 8,143 adolescents (2011 = 3,992 adolescents; 2016 = 4,151 adolescents).

The criteria adopted for inclusion of participants in the research were the following: being regularly enrolled in the 1st to 3rd year classes of High School of the selected schools; being present at the time of application of the instrument; adequately complete the distributed questionnaire. The adolescents’ participation in the study was voluntary and anonymous.

Regarding ethical aspects, the research was authorized by the State Secretary of Education, the directors of the Regional Education Directorates and the directors of the Teaching Units surveyed. In addition, the signing of the Free and Informed Consent Form by the parents of the students and the signing of the Assent Form by the students. The surveys were approved by the Ethics Committee for Research with Human Beings CEP/CONEP/CNS, under protocol no. 177/2010 CEP/HU/UFS and no. 1,522,876/2016 CEP/IFS, respectively.

The questionnaire used was a version of the Global School-based Student Health Survey , proposed by the World Health Organization ( GSHS/WHO).) to collect information regarding sociodemographic and economic aspects, level of physical activity, and exposure to sedentary behavior. Data collection was performed by applying a questionnaire by two properly trained researchers. The average application time in each class was 45 minutes.

The outcome variable of the study was ECS; and the independent variables were: age, sex, place of residence, maternal education, monthly family income (minimum wage), and source of income. Adolescents who spent more than or equal to two hours on screens, such as watching television, using the computer, playing video games, talking to friends, or similar activities, were considered “exposed to sedentary behavior” ² .

For statistical treatment, the variables were analyzed using descriptive and inferential procedures. In the bivariate association analysis, the chi-square test for heterogeneity was used. In the multivariate analysis, crude binary logistic regression was used, adjusted for the study outcomes.

Variables with p<0.20 in the crude analysis were included in the adjusted model, and the significance level adopted was 5%. The SPSS 22.0 statistical program was used.

RESULTS

A total of 9,438 adolescents responded to the research instrument (2011 = 4,717; 2016 = 4,721). People over 19 years of age (2011 = 709; 2016 = 549), under 14 years of age (2011 = 08; 2016 = 12), who did not inform their age (2011 = 02; 2016 = 06), who did not inform their gender (2011 = 03; 2016 = 12) and who failed to complete several questions in the collection instrument (2011 = 11; 2016 = 03) were excluded from the sample. The final sample consisted of 8,143 (2011 = 3,992; 2016 = 4,151).

Table 1 shows the demographic and socioeconomic characteristics of the sample. Most students were 16 and 17 years old, were female, lived in urban areas, had mothers with primary education and had a source of income from their father’s and/or mother’s work. A reduction in the purchasing power of families with a monthly income above 1 minimum wage was observed.

Table 2 shows the relationship between ECS and demographic and socioeconomic characteristics. A higher prevalence was found in adolescents aged 14 and 15 years, female, living in urban areas, whose mothers had secondary or higher education, who had a monthly family income above two minimum wages and whose source of income came from a pension in both surveys.

Table 3 shows the crude and adjusted association between ECS and demographic and socioeconomic conditions. In the adjusted analysis, an association with age, sex, place of residence, maternal education and monthly family income was found in both surveys.

DISCUSSION

The study presented the prevalence of adolescents with ECS, in addition to the association of this behavior with socioeconomic and demographic indicators in the State of Sergipe. A considerable prevalence of adolescents exposed to sedentary behavior was observed, being higher in schoolchildren aged 14 and 15 years, female, living in urban areas, who have mothers with high school and/or higher education, with a monthly family income above two minimum wages and a source of income from a pension in both surveys.

It was found that 46.2% (2011) and 44.8% (2016) of adolescents were exposed to more than two hours of sitting, watching TV, using the computer, talking to friends, playing cards or dominoes. The outcome is consistent with an international investigation that reported a high prevalence of young people using screen time in 34 countries in the Americas ¹³ . National studies have also shown that in Pernambuco, 40.9% of schoolchildren ¹⁴ , in Pelotas-RS, 79.7% of adolescents ¹⁵ and throughout the country, 60% of adolescents were exposed to sedentary behavior ¹⁰ .

Adolescents aged 14 and 15 years had a higher prevalence of ECS (2011 = 52.7%; 2016 = 51.1%) and higher chances of ECS when compared to other age groups. It was noted that the percentage of adolescents exposed to this behavior decreases as they age, unlike investigations in Greece-Cyprus ¹⁶ and in Pernambuco, Brazil ¹⁴ .

Girls had a high prevalence (2011 = 48.8% / 2016 = 46.7%) for ECS, according to studies in Greece-Cyprus ¹⁶ and in southern Brazil ¹⁷ . It was also found that female adolescents have a higher chance of ECS when compared to boys ¹⁸ . This can be explained by sociocultural aspects that reduce the possibilities of girls to practice physical activity ¹⁹ .

Adolescents living in urban areas had a higher prevalence (2011 = 50%; 2016 = 49.7%) and greater chances of ECS in relation to those living in rural areas, unlike studies in Portugal ²⁰ and Saudi Arabia ²¹ .

There was a relationship between higher maternal education (high school and higher education) and increased sedentary behavior, according to a study in the United Kingdom ²² . The fact that parents with a higher level of education encourage adolescents to spend more time studying ²³ may contribute to sedentary activities.

A relationship was also observed between higher monthly family income (above two minimum wages) and increased sedentary behavior. The association between sedentary behavior and socioeconomic status was also observed in a cross-sectional study in Mato Grosso ²⁴ .

Increased family purchasing power is an important factor in sedentary behavior in children and adolescents ^15,25,26 , such as the purchase of electronic devices for adolescents ²² , favoring sedentary activities. In this sense, a trend study showed an increase in the prevalence of computer and video game use between 2001 and 2011 among adolescents in Santa Catarina ²⁷ .

CONCLUSION

It was concluded that there was a trend toward a reduction in ECS in adolescents from a state in northeastern Brazil between 2011 and 2016. A higher prevalence of ECS was observed in adolescents aged 14 to 15 years, females, and living in urban areas. ECS in adolescents was associated with age, sex, place of residence, and maternal education in both surveys. Therefore, we suggest the development of public policies to reduce ECS and provide opportunities for adolescents to build healthy lifestyles.