Social networks, social isolation and leisure-time physical activity in Brazilian adolescent students

Redes sociais, isolamento social e atividade física no lazer entre adolescentes estudantes brasileiros

Redes sociales, aislamiento social y actividad física en el tiempo libre en adolescentes escolares brasileños

Abstract

The objective of this article is to investigate the association between social networks, social isolation, and leisure-time physical activity among Brazilian schoolchildren. This national cross-sectional study included 101,927 9^th-grade students (aged 13-15) from 3,040 schools. Leisure-time physical activity was assessed based on frequency and duration over the previous seven days and categorized into four levels: ≥300, 150-299, 1-149, and 0 minutes per week. Social isolation and social networks were measured by the frequency of feeling lonely and the number of close friends. Multinomial logistic regression estimated unadjusted and adjusted odds ratios. After adjusting for sociodemographic and behavioral factors, students who always felt isolated had 26% higher odds of being completely inactive compared to those who never felt isolated. Those with no close friends had 69% higher odds of complete inactivity versus those with three or more friends. Health promotion initiatives should address the role of peer relationships and social connectedness in shaping adolescents’ physical activity patterns.

Key words:
Social Isolation; Social Networks; Leisure-Time Physical Activity; Adolescents; Schoolchildren

Resumo

O objetivo deste artigo é investigar a associação entre redes sociais, isolamento social e atividade física no lazer em escolares brasileiros. Este estudo transversal nacional incluiu 101.927 estudantes do 9º ano (13 a 15 anos) de 3.040 escolas. A atividade física no lazer foi avaliada com base na frequência e duração nos últimos sete dias e categorizada em quatro níveis: ≥300, 150 a 299, 1 a 149 e 0 minutos por semana. O isolamento social e as redes sociais foram medidos pela frequência de sentimento de solidão e pelo número de amigos próximos. Regressão logística multinomial foi utilizada para estimar as razões de chances brutas e ajustadas. Após o ajuste para fatores sociodemográficos e comportamentais, os estudantes que sempre se sentiram isolados apresentaram chances 26% maiores de serem completamente inativos em comparação com aqueles que nunca se sentiram isolados. Aqueles sem amigos próximos apresentaram probabilidade 69% maior de inatividade completa em comparação com aqueles com três ou mais amigos. Iniciativas de promoção da saúde devem abordar o papel dos relacionamentos entre pares e da conexão social na formação dos padrões de atividade física no lazer dos adolescentes.

Palavras-chaves:
Isolamento Social; Redes Sociais; Atividade Física no Lazer; Adolescentes; Escolares

Resumen

El objetivo de este artículo es evaluar la asociación entre redes sociales, aislamiento social y la práctica de actividad física durante el tiempo libre entre escolares brasileños. Estudio transversal de base nacional, que incluyó a 101.927 estudiantes del noveno grado (entre 13 y 15 años) provenientes de 3.040 escuelas. La actividad física en el tiempo libre fue medida en función de su frecuencia y duración en los siete días previos, y categorizada en cuatro niveles: ≥300, 150-299, 1-149 y 0 minutos por semana. El aislamiento social y las redes sociales se evaluaron a partir de la frecuencia con la que el estudiante se sentía solo y del número de amigos cercanos. Se estimaron razones de probabilidad (odds ratios) crudas y ajustadas mediante regresión logística multinomial. Tras el ajuste por factores sociodemográficos y conductuales, los estudiantes que siempre se sentían aislados tuvieron un 26% más de probabilidades de estar completamente inactivos, en comparación con aquellos que nunca se sentían aislados. Los que no tenían amigos cercanos presentaron un 69% más de probabilidades de inactividad total, en relación con quienes tenían tres o más amigos. Las intervenciones de promoción de la salud en adolescentes deben contemplar el fortalecimiento de las relaciones interpersonales y del sentido de pertenencia social, como componentes relevantes para incentivar la actividad física.

Palabras clave:
Aislamiento Social; Redes Sociales; Actividad Física en el Tiempo Libre; Adolescentes; Escolares

Introduction

Low physical activity among adolescents is a global public health concern. In 2016, nearly 80% of the world’s adolescents aged 11 and 17 were considered insufficiently active¹. In Brazil, only 34.4% of 9th graders were classified as physically active in 2015².

Among school-age youth, physical inactivity is associated with increased cardiometabolic risk, higher levels of body fat, lower fitness and compromised bone health³. Additionally, insufficient physical inactivity during adolescence is a strong predictor of continued inactivity in later life⁴. Physically inactive children are more likely to exhibit biological risk factors such as high blood pressure, elevated cholesterol levels, and increased body fat⁵. Conversely, the risk of developing cardiovascular disease decreases progressively with increased physical activity⁶.

Brazilian studies have consistently shown a high prevalence of physical inactivity among adolescents. Despite variations in criteria and cutoff points, the prevalence of physical inactivity ranges from 55.9% to 82.7% across different Brazilian cities^7-10.

Overall, girls, older adolescents, and those with lower education attainment, and individuals from lower socioeconomic backgrounds have been identified as less active^7,8,11,12. Physical inactivity in children and adolescents is also associated with risky health behaviors, including unhealthy eating, sedentary behavior, smoking, alcohol consumption, and drug use^8,13.

Social support, defined as the resources provided individuals within one’s social network, has been linked with physical activity in adolescents⁴. Longitudinal studies have shown that logistical support, parental role modeling and having active friends are positive factors that encourage young people remain active^14,15. However, as adolescents age, the influence of family tends to decrease while peer influence becomes more prominent¹⁶. The physical activity levels of friends positively influence adolescents, with those having active friends being more likely to be active themselves¹⁶. On the other hand, limited social networks can act as a barrier to engaging in physical activity¹⁷. Research on adolescents has demonstrated that feelings of loneliness and having few friends are characteristics associated with physical inactivity^18-20. While several systematic reviews have explored the relationship between adolescent physical activity and the support of parents and friends, less than 1% of the studies have been conducted Brazil^14,16,21-24. Therefore, the aim of this study is to investigate the potential association between social networks, social isolation and physical inactivity among Brazilian adolescent students.

Methods

The present study utilized data from the third edition of the National Adolescent School-based Health Survey (PeNSE-2015), which monitors health risk factors among Brazilian students. The PeNSE-2015 is a cross-sectional, school-based study with data collected through self-administered electronic questionnaires from April to September 2015. Data are publicly available and can be accessed through the Brazilian Institute of Geography and Statistics (IBGE) website².

Sampling plan included 9^th grade students from public and private schools across Brazil in 2015. The age range of the students was 13 to 15 years, a reference group for school surveys. This age group represents the the minimum age suitable for responding to self-administered questionnaires². According to IBGE, approximately 2.6 million students were enrolled in fundamental school in Brazil in 2015.

The 2015 PeNSE sample was randomly selected from 53 geographical strata: including 26 state capitals and Federal District, as well as the 26 states. Schools within each stratum were selected based on the 2013 School Census, and within each selected school, 9^th-grade classes were randomly selected with probability proportional to size. Thus, the primary sampling units were the schools and the secondary units were the classes, resulting in an independent sample of students in each stratum. All students present in the selected classes were eligible and invited to participate in the study².

The inclusion criteria were to be enrolled in the 9^th year of elementary school, during the 2015 academic year, and regularly attending public or private schools located in urban or rural areas of the National Territory. Night shift students and schools with fewer than 15 students enrolled in the 9^th grade in 2013 were excluded².

The sample size for each geographic stratum was calculated to provide estimates of proportions (or prevalence) for selected characteristics of interest, with a maximum sampling error of approximately 3 percentage points and a 95% confidence level. A prevalence of 50% was used in the calculation. The number of schools was obtained by dividing the number of 9^th grade classes in the sample by the average number of 9^th grade classes per school in each stratum. Sample weights accounted for the sizes of schools, classes, and students. Based on this sample design, the analysis included 101,500 students from 3,040 schools.

To ensure quality and standardization of data collection, IBGE state supervisors were trained and, in turn, provided training to the interviewers.

Leisure-time physical activity levels among students over the past seven days were assessed using questions on the frequency and duration of extracurricular activities, such as sports, dance, gymnastics, weight training, and martial arts. These questions were adapted from the International Physical Activity Questionnaire (IPAQ), a tool with established reliability and validity²⁵. Based on weekly accumulated minutes, physical activity was categorized into four levels: ≥300 minutes per week (m/w), 150-299m/w, 1-149m/w and zero m/w²⁶.

The main exposures were social isolation and physical social network. Social isolation was assessed with a question on how often adolescents felt lonely (never/rarely/sometimes/most of the time/always), and the social network was assessed by asking about the number of close friends they had (no friends/one friend/two friends/three or more friends).

Confounding factors included demographic, socioeconomic and behavioral variables. Demographics were gender (male/female), skin color (white/black/brown/indigenous/yellow), and age (11 to 13 years/14 years/15 years/16 years/17 years or older). Socioeconomic status was determined based on maternal education (did not study/incomplete elementary school/complete elementary school/incomplete high school/complete high school/incomplete undergraduate education or more).

Behavioral characteristics included: frequency of vegetable consumption per week (zero/1 to 3 days/4 to 6 days/every day), smoking status (non-smoker/smoker), number of alcoholic drinks consumed in the last month (none/less than 1 glass/1 to 2 glasses/3 to 4 glasses/5 glasses or more), use of illicit drugs (cannabis, cocaine and inhalants) in the last month (did not use/used) and daily sitting time (≤2hs/>2hs/day).

Data were analyzed using Stata version 15 (StataCorp, College Station, TX, USA). Descriptive analyses were conducted to calculate absolute and relative frequencies. Univariate associations between categorical variables were assessed using the chi-square test for linear trend. Polytomous (multinomial) logistic regression was employed instead of ordered logistic regression due to concerns regarding the proportional odds assumption. Although the outcome categories of physical activity levels have an inherent order (from high activity to complete inactivity), the Brant test revealed a statistically significant violation of the proportional odds assumption for both exposures, an essential requirement for the validity of ordered logistic models.

In contrast, multinomial logistic regression does not impose this assumption and allows for greater flexibility by estimating separate odds ratio for each level of the outcome relative to the reference category (≥300 minutes/week). For the multivariable analysis, a confounding control strategy was adopted. Variables were considered confounders if they were significantly associated with both the exposure and the outcome (p<0.05) and were not hypothesized to lie on the causal pathway. All analyses accounted for the complex survey design, incorporating primary sampling units (schools), geographic strata, and sampling weights. Analyses were performed for the total sample and stratified by sex. A significance level of 1% (p<0.01) was adopted to identify statistically significant associations.

The PeNSE-2015 study was approved by the National Research Ethics Committee (CONEP) of the National Health Council (CNS), under approval number 1.006.467, on March 3, 2015.

Results

Our analysis included 101,927 students, comprising 49,218 boys and 52,709 girls. Among Brazilian adolescents, leisure-time physical activity levels varied considerably by sex and across sociodemographic, behavioral, and psychosocial characteristics. Overall, only 15.7% (95%CI: 15.3-16.2) of students engaged in ≥300 minutes/week of extracurricular physical activity (Table 1), with a marked sex disparity: 22.7% (95%CI: 22.0-23.5) among boys (Table 2) and 9.1% (95%CI: 8.6-9.6) among girls (Table 3). In contrast, complete inactivity (0 minutes/week) was reported by 34.6% (95%CI: 33.9-35.3) of the overall sample, with significantly higher prevalence among girls (43.9%, 95%CI: 43.0-44.9) compared to boys (24.8%, 95%CI: 24.0-25.6). Higher levels of physical activity were generally associated with younger age, higher maternal education, healthier eating habits (e.g., fruit and vegetable consumption), and stronger social networks (i.e., having three or more close friends and low levels of social isolation). Conversely, lower physical activity levels were more common among adolescents who reported frequent social isolation, fewer close friends, greater screen time, and lower parental education (Tables 1, 2 and 3).

Table 1
Distribution of leisure-time physical activity levels by sociodemographic, behavioral, and psychosocial characteristics among Brazilian adolescents.

Variable	n	%≥300m/w [IC95%]	%150 to 299 m/w [IC95%]	%1 to 149 m/w [IC95%]	%0 m/w [IC95%]
Leisure-time physical activity	101,927	15.7[15.3-16.2]	13.3[12.8 -13.8]	36.4 [35.7 -37.0]	34.6 [33.9-35.3]
Sex
Male	49,218	22.7[22.0-23.5]	16.9 [16.2-17.6]	35.6 [34.7-36.4]	24.8 [24.0-25.6]
Female	52,709	9.1 [8.6-9.6]	9.9 [9.3-10.4]	37.1 [36.3-37.9]	43.9 [43.0-44.9]
Age
11 to 13 years	17,235	14.4 [13.3-15.4]	14.6 [13.5-15.8]	37.9 [36.3-39.4]	33.2 [31.7-34.6]
14 years	51,542	15.6 [15.0-16.3]	14.0 [13.4-14.6]	36.1 [35.3-36.9]	34.3 [33.4-35.2]
15 years	20,842	17.4 [16.4-18.5]	11.2 [10.5-11.9]	36.7 [35.5-38.0]	34.6 [33.4-35.8]
16 years	7,852	16.1 [14.7-17.5]	12.3 [11.0-13.7]	34.1 [32.2-36.0]	37.6 [35.6-39.7]
≥17 years	4,456	14.7 [13.2-16.4]	10.4 [9.0-11.9]	34.7 [32.5-36.9]	40.2 [37.8-42.6]
Skin color
White	33,725	15.9 [15.2-16.6]	14.2 [13.5-15.0]	35.9 [34.9-36.8]	34.0 [32.8-35.2]
Black	12,827	17.2 [16.0-18.4]	13.2 [12.0-14.5]	35.6 [34.1-37.2]	34.0 [32.5-35.6]
Brown	46,879	15.2 [14.5-15.8]	12.6 [12.0-13.2]	37.1 [36.2-38.0]	35.2 [34.3-36.2]
Indigenous	4,569	14.7 [13.1-16.6]	13.1 [11.4-15.1]	34.8 [32.5-37.3]	37.3 [35.0-39.7]
Yellow	3,823	17.5 [15.5-19.7]	13.6 [11.8-15.6]	37.8 [35.1-40.7]	31.1 [28.5-33.8]
Maternal education
Incomplete higher education or more	22,676	20.2 [19.3-21.2]	18.4 [17.4-19.5]	34.2 [33.0-35.5]	27.1 [25.7-28.5]
Complete high school	17,889	17.5 [16.5-18.5]	14.2 [13.2-15.2]	35.0 [33.9-36.2]	33.3 [32.1-34.6]
Incomplete high school	6,268	14.3 [12.9-15.9]	14.6 [13.0-16.3]	37.4 [35.4-39.5]	33.7 [31.7-35.7]
Complete elementary school	6,012	15.2 [13.6-16.9]	13.2 [11.6-15.0]	37.7 [35.5-39.9]	33.9 [31.8-36.1]
Incomplete elementary school	18,191	14.3 [13.4-15.3]	11.2 [10.3-12.0]	39.4 [38.2-40.6]	35.1 [33.9-36.4]
Did not study	5,516	12.2 [10.9-13.7]	9.0 [7.8-10.4]	37.9 [35.7-40.1]	40.9 [38.7-43.1]
Fruit & vegetable per week
Everyday	9,957	27.4 [25.8-28.9]	15.6 [14.3-17.1]	31.6 [30.0-33.3]	25.4 [23.8-27.0]
5-6 days	9,117	22.7 [21.0-24.5]	18.3 [16.9-19.7]	36.1 [34.2-38.0]	22.9 [21.4-24.6]
3-4 days	19,699	17.2 [16.2-18.2]	17.7 [16.6-18.8]	39.5 [38.1-40.8]	25.7 [24.5-26.9]
1-2 days	30,200	12.6 [12.0-13.3]	12.3 [11.5-13.0]	40.9 [39.9-42.0]	34.2 [33.0-35.3]
Never	32,852	12.0 [11.4-12.6]	9.2 [8.6-9.8]	31.5 [30.5-32.5]	47.3 [46.3-48.4]
Smoking status
Non smoker	96,461	15.7 [15.3-16.2]	13.3 [12.8-13.8]	36.6 [36.0-37.2]	34.4 [33.7-35.1]
Smoker	5,408	16.2 [14.5-18.0]	12.9 [11.2-14.9]	32.7 [30.3-35.1]	38.2 [35.6-40.9]
Alcohol consumption last month
None	76,872	15.2 [14.7-15.7]	13.2 [12.7-13.8]	36.8 [36.1-37.5]	34.8 [34.0-35.6]
<1 glass	6,664	15.6 [14.2-17.2]	12.5 [11.1-14.0]	37.7 [35.5-39.9]	34.2 [31.9-36.5]
1-2 glasses	9,584	16.4 [15.1-17.8]	13.0 [12.0-14.2]	37.0 [35.2-38.7]	33.6 [31.9-35.3]
3-4 glasses	3,999	17.8 [15.9-19.9]	15.7 [13.7-18.0]	34.1 [31.5-36.8]	32.3 [29.7-35.1]
≥5 glasses	4,659	21.8 [19.9-23.8]	13.7 [11.9-15.7]	28.3 [25.6-31.2]	36.2 [33.4-39.0]
Illicit drug use
No	97,980	15.6 [15.2-16.1]	13.3 [12.8-13.8]	36.6 [35.9-37.2]	34.5 [33.8-35.2]
Yes	3,905	18.8 [16.6-21.2]	12.8 [10.7-15.2]	31.8 [28.9-34.9]	36.7 [33.8-39.6]
Sedentary behavior
≤2 hs/ day	33,196	16.1 [15.4-16.9]	11.8 [11.1-12.5]	38.7 [37.7-39.8]	33.3 [32.2-34.5]
>2 hs/ day	68,124	15.6 [15.1-16.1]	14.1 [13.5-14.7]	35.3 [34.7-36.0]	35.0 [34.2-35.8]
Social Isolation
Never	34,299	19.5 [18.7-20.4]	13.6 [12.9-14.4]	36.8 [35.9-37.8]	30.0 [29.0-31.1]
Rarely	21,824	16.7 [15.8-17.6]	15.5 [14.6-16.4]	36.4 [35.2-37.7]	31.4 [30.0-32.7]
Sometimes	28,366	12.0 [11.4-12.6]	12.4 [11.7-13.1]	37.9 [36.9-38.9]	37.7 [36.6-38.8]
Most of the time	10,696	12.2 [11.1-13.5]	12.8 [11.7-14.1]	34.4 [32.8-36.1]	40.5 [38.7-42.4]
Always	6,347	14.2 [12.6-15.9]	9.2 [7.9-10.6]	30.5 [28.3-32.8]	46.1 [43.9-48.4]
Social network
≥3 friends	77,922	16.7 [16.2-17.2]	13.9 [13.4-14.4]	36.6 [35.9-37.3]	32.8 [32.1-33.6]
2 friends	12,958	12.7 [11.8-13.7]	12.5 [11.5-13.7]	36.1 [34.6-37.7]	38.6 [37.0-40.2]
1 friend	6,460	11.2 [9.8-12.8]	10.5 [9.3-11.8]	35.4 [33.2-37.6]	42.9 [40.6-45.4]
No friend	4,168	14.3 [12.5-16.3]	10.0 [8.6-11.7]	35.3 [32.5-38.3]	40.4 [37.5-43.3]

• Note: Values in bold indicate statistical significance at the p<0.01 level.
• Source: Authors.

Table 2
Distribution of leisure-time physical activity levels by sociodemographic, behavioral, and psychosocial characteristics among male Brazilian adolescents.

Variable	n	%≥300m/w [IC95%]	%150 to 299 m/w [IC95%]	%1 to 149 m/w [IC95%]	%0 m/w [IC95%]
Leisure-time physical activity	49,218	22.7 [22.0-23.5]	16.9 [16.2-17.6]	35.6 [34.7-36.4]	24.8 [24.0-25.6]
Age
11 to 13 years	7,156	22.3 [20.6-24.1]	19.0 [17.1-21.1]	35.3 [32.9-37.7]	23.4 [21.4-25.6]
14 years	23,701	23.1 [22.0-24.2]	18.0 [17.0-19.0]	35.1 [33.9-36.2]	23.8 [22.7-25.0]
15 years	11,184	23.7 [22.3-25.2]	14.3 [13.2-15.5]	37.0 [35.3-38.8]	25.0 [23.7-26.3]
16 years	4,624	21.4 [19.5-23.4]	15.5 [13.8-17.5]	35.0 [32.8-37.3]	28.0 [25.7-30.5]
≥17 years	2,553	18.5 [16.4-20.7]	13.1 [11.2-15.2]	35.3 [32.5-38.3]	33.1 [29.9-36.5]
Skin color
White	16,973	22.4 [21.3-23.6]	17.4 [16.3-18.5]	35.2 [34.0-36.4]	25.0 [23.7-26.4]
Black	7,180	23.2 [21.4-25.0]	16.4 [14.7-18.3]	34.4 [32.4-36.5]	26.0 [24.2-27.9]
Brown	21,129	22.9 [21.9-23.9]	16.7 [15.7-17.7]	36.3 [35.0-37.6]	24.1 [22.9-25.3]
Indigenous	1,858	21.9 [18.9-25.2]	16.2 [13.2-19.7]	36.2 [32.6-39.9]	25.8 [22.5-29.4]
Yellow	2,020	23.5 [20.3-26.9]	18.0 [15.2-21.3]	35.1 [31.4-38.9]	23.4 [20.5-26.6]
Maternal education
Incomplete higher education or more	11,374	26.6 [25.1-28.2]	21.7 [20.3-23.1]	32.4 [31.0-33.9]	19.3 [17.9-20.8]
Complete high school	8,697	24.8 [23.1-26.5]	18.6 [17.2-20.2]	34.1 [32.3-35.9]	22.5 [20.9-24.1]
Incomplete high school	2,853	22.4 [19.8-25.1]	19.8 [17.1-22.9]	35.9 [32.8-39.2]	21.9 [19.4-24.6]
Complete elementary school	3,068	22.3 [19.6-25.2]	17.2 [14.8-20.0]	37.4 [34.3-40.6]	23.1 [20.6-25.7]
Incomplete elementary school	7,966	21.6 [20.0-23.1]	14.7 [13.5-16.1]	37.5 [35.9-39.2]	26.2 [24.6-27.8]
Did not study	2,510	18.4 [15.9-21.3]	10.5 [8.5-12.8]	39.3 [36.0-42.7]	31.8 [28.6-35.3]
Fruit &vegetable per week
Everyday	4,861	35.6 [33.1-38.1]	16.2 [14.5-18.1]	28.9 [26.7-31.3]	19.3 [17.4-21.3]
5-6 days	4,494	32.4 [29.8-35.1]	22.3 [20.1-24.6]	29.5 [27.0-32.3]	15.7 [14.0-17.6]
3-4 days	10,189	24.8 [23.5-26.3]	22.0 [20.4-23.7]	35.3 [33.6-37.1]	17.8 [16.5-19.1]
1-2 days	14,552	18.7 [17.5-19.9]	16.1 [14.8-17.4]	41.8 [40.3-43.3]	23.5 [22.1-24.9]
Never	15,046	18.0 [16.9-19.2]	12.7 [11.8-13.6]	33.6 [32.2-35.1]	35.7 [34.4-37.1]
Smoking status
Non smoker	46,355	22.8 [22.1-23.6]	17.0 [16.3-17.7]	35.7 [34.9-36.5]	24.5 [23.7-25.3]
Smoker	2,824	21.3 [18.7-24.2]	16.0 [13.6-18.7]	33.2 [29.9-36.8]	29.5 [26.2-32.9]
Alcohol consumption last month
None	37,879	21.7 [20.9-22.5]	16.7 [16.0-17.4]	36.1 [35.2-37.0]	25.5 [24.5-26.5]
<1 glass	2,777	24.4 [21.8-27.3]	15.6 [13.3-18.2]	37.1 [33.9-40.5]	22.8 [20.3-25.5]
1-2 glasses	4,303	24.4 [22.3-26.6]	17.5 [15.6-19.5]	36.8 [34.4-39.3]	21.3 [19.3-23.4]
3-4 glasses	1,831	26.1 [22.8-29.7]	20.9 [17.8-24.5]	31.7 [28.0-35.6]	21.3 [18.2-24.7]
≥5 glasses	2,335	31.4 [28.3-34.7]	17.6 [14.9-20.8]	25.5 [22.6-28.6]	25.5 [22.5-28.7]
Illicit drug use
No	47,043	22.6 [21.9-23.3]	17.0 [16.3-17.7]	35.7 [34.9-36.5]	24.7 [23.9-25.5]
Yes	2,149	25.3 [21.9-29.0]	15.2 [12.2-18.9]	32.1 [28.5-36.0]	27.4 [23.6-31.5]
Sedentary behavior
≤2 hs/ day	16,240	22.6 [21.5-23.8]	14.8 [13.8-16.0]	37.5 [36.1-38.9]	25.1 [23.8-26.4]
>2 hs/ day	32,632	22.9 [22.1-23.8]	18.1 [17.2-19.0]	34.8 [33.8-35.8]	24.3 [23.2-25.3]
Social Isolation
Never	21,817	25.1 [24.1-26.2]	15.9 [15.0-16.9]	35.1 [33.9-36.3]	23.8 [22.6-25.0]
Rarely	11,105	23.3 [22.0-24.7]	19.7 [18.4-21.0]	35.4 [33.7-37.2]	21.6 [20.2-23.1]
Sometimes	10,950	19.3 [17.8-20.8]	17.3 [16.1-18.6]	38.2 [36.7-39.8]	25.2 [23.8-26.7]
Most of the time	3,225	17.7 [15.5-20.2]	18.0 [15.6-20.6]	34.2 [31.0-37.5]	30.1 [27.0-33.4]
Always	1,842	21.7 [18.2-25.6]	10.5 [8.1-13.4]	29.9 [26.1-34.0]	37.9 [34.2-41.8]
Social network
≥3 friends	38,779	23.9 [23.1-24.7]	17.3 [16.6-18.1]	35.4 [34.6-36.3]	23.4 [22.5-24.2]
2 friends	5,131	19.4 [17.7-21.1]	17.8 [15.9-19.8]	37.2 [34.9-39.6]	25.6 [23.6-27.7]
1 friend	2,704	17.0 [14.2-20.2]	14.7 [12.4-17.4]	35.5 [32.4-38.8]	32.8 [29.1-36.7]
No friend	2,314	19.6 [16.8-22.8]	12.2 [10.0-14.8]	35.5 [31.8-39.4]	32.7 [29.4-36.3]

• Note: Values in bold indicate statistical significance at the p<0.01 level.
• Source: Authors.

Table 3
Distribution of leisure-time physical activity levels by sociodemographic, behavioral, and psychosocial characteristics among female Brazilian adolescents.

Variable	n	%≥300m/w [IC95%]	%150 to 299 m/w [IC95%]	%1 to 149 m/w [IC95%]	%0 m/w [IC95%]
Leisure-time physical activity	52,709	9.09 [8.6-9.6]	9.9 [9.3-10.4]	37.1 [36.3-37.9]	43.9 [43.0-44.9]
Age
11 to 13 years	10,079	8.5 [7.4-9.6]	11.3 [10.1-12.6]	39.8 [37.9-41.7]	40.4 [38.3-42.5]
14 years	27,841	9.1 [8.5-9.7]	10.5 [9.8-11.3]	36.9 [35.9-37.9]	43.4 [42.2-44.6]
15 years	9,658	9.9 [8.8-11.2]	7.5 [6.7-8.4]	36.4 [34.7-38.1]	46.2 [44.4-47.9]
16 years	3,228	8.3 [6.9-10.0]	7.5 [6.2-9.0]	32.7 [30.0-35.5]	51.5 [48.3-54.6]
≥17 years	1,903	9.9 [7.9-12.4]	6.9 [5.1-9.2]	33.8 [30.4-37.4]	49.4 [45.5-53.3]
Skin color
White	16,752	9.2 [8.4-10.1]	11.1 [10.2-12.0]	36.5 [35.1-37.9]	43.2 [41.5-44.9]
Black	5,647	9.4 [7.9-11.1]	9.0 [7.6-10.6]	37.2 [35.0-39.5]	44.4 [42.2-46.7]
Brown	25,750	8.8 [8.2-9.4]	9.2 [8.5-9.9]	37.7 [36.6-38.8]	44.4 [43.2-45.6]
Indigenous	2,711	9.5 [7.9-11.5]	10.9 [8.8-13.2]	33.9 [30.8-37.1]	45.7 [42.6-49.0]
Yellow	1,803	10.7 [8.5-13.3]	8.5 [6.4-11.2]	41.0 [36.7-45.3]	39.9 [35.8-44.2]
Maternal education
Incomplete higher education or more	11,302	13.8 [12.5-15.1]	15.1 [13.8-16.6]	36.1 [34.1-38.1]	35.0 [33.0-37.1]
Complete high school	9,192	10.3 [9.3-11.5]	9.8 [8.7-11.0]	36.0 [34.3-37.6]	43.9 [42.2-45.7]
Incomplete high school	3,415	7.4 [6.0-9.2]	10.1 [8.4-12.0]	38.7 [35.9-41.6]	43.8 [40.7-47.0]
Complete elementary school	2,944	7.7 [6.3-9.4]	9.0 [7.3-11.1]	38.0 [35.2-41.0]	45.3 [42.1-48.6]
Incomplete elementary school	10,225	8.5 [7.6-9.6]	8.3 [7.4-9.2]	40.9 [39.2-42.6]	42.3 [40.6-44.1]
Did not study	3,006	6.9 [5.7-8.3]	7.7 [6.1-9.7]	36.6 [34.0-39.3]	48.8 [46.0-51.6]
Fruit &vegetable per week
Everyday	5,096	19.3 [17.6-21.1]	15.1 [13.3-17.0]	34.3 [31.9-36.7]	31.4 [29.0-33.8]
5-6 days	4,623	13.6 [12.1-15.3]	14.5 [12.7-16.5]	42.2 [39.6-44.8]	29.7 [27.3-32.3]
3-4 days	9,510	9.0 [8.0-10.1]	13.0 [11.8-14.4]	43.9 [41.9-45.9]	34.1 [32.1-36.0]
1-2 days	15,648	6.8 [6.1-7.5]	8.6 [7.8-9.4]	40.1 [38.7-41.7]	44.5 [42.9-46.1]
Never	17,806	6.8 [6.2-7.5]	6.3 [5.7-6.9]	29.7 [28.5-30.9]	57.2 [55.9-58.6]
Smoking status
Non smoker	50,106	9.0 [8.5-9.5]	9.9 [9.3-10.4]	37.4 [36.6-38.2]	43.8 [42.8-44.7]
Smoker	2,584	10.9 [8.9-13.2]	9.8 [8.0-12.0]	32.1 [28.7-35.7]	47.2 [43.4-51.1]
Alcohol consumption last month
None	38,993	8.6 [8.1-9.2]	9.8 [9.2-10.4]	37.5 [36.6-38.4]	44.2 [43.2-45.2]
<1 glass	3,887	9.2 [7.9-10.8]	10.2 [8.6-12.1]	38.1 [35.5-40.8]	42.5 [39.6-45.3]
1-2 glasses	5,281	10.0 [8.7-11.4]	9.5 [8.1-11.0]	37.1 [34.7-39.6]	43.5 [41.0-46.0]
3-4 glasses	2,168	10.8 [8.9-13.1]	11.4 [9.2-13.9]	36.1 [32.5-39.9]	41.7 [37.6-45.8]
≥5 glasses	2,324	12.7 [10.7-15.0]	10.0 [8.0-12.3]	31.0 [26.9-35.4]	46.3 [42.0-50.8]
Illicit drug use
No	50,937	9.0 [8.5-9.5]	9.9 [9.3-10.4]	37.3 [36.6-38.1]	43.8 [42.9-44.7]
Yes	1,756	11.0 [8.8-13.7]	9.8 [7.3-12.9]	31.4 [27.1-36.0]	47.8 [43.4-52.3]
Sedentary behavior
≤2 hs/ day	16,956	9.7 [8.9-10.6]	8.8 [8.0-9.6]	40.0 [38.6-41.4]	41.6 [40.1-43.1]
>2 hs/ day	35,492	8.8 [8.3-9.4]	10.4 [9.7-11.0]	35.9 [34.9-36.9]	44.9 [43.8-46.0]
Social Isolation
Never	12,482	9.5 [8.7-10.5]	9.5 [8.6-10.4]	39.9[38.4-41.5]	41.1[39.6-42.7]
Rarely	10,719	9.8 [8.8-12.5]	11.2 [10.0-12.5]	37.5[35.8-39.2]	41.5[39.6-43.4]
Sometimes	17,416	7.6 [7.0 - 8.2]	9.3 [8.6-10.2]	37.7[36.5-39.0]	45.4[44.1-46.7]
Most of the time	7,471	9.8 [8.7-11.2]	10.6 [9.4-12.0]	34.5[32.6-36.4]	45.1[42.9-47.2]
Always	4,505	11.0 [9.4-12.8]	8.6 [7.2-10.3]	30.8[28.4-33.2]	49.6[47.1-52.1]
Social network
≥3 friends	39,143	9.7 [9.0-10.1]	10.4 [9.8-11.0]	37.8 [36.8-38.7]	42.3 [41.2-43.3]
2 friends	7,827	8.2 [7.2-9.2]	9.0 [7.9-10.3]	35.4 [33.6-37.3]	47.4 [45.3-49.5]
1 friend	3,756	7.0 [5.7-8.6]	7.5 [6.2-9.0]	35.2 [32.4-38.2]	50.3 [47.0-53.5]
No friend	1,854	7.1 [5.5-9.2]	7.2 [5.4-9.5]	35.1 [30.9-39.5]	50.6 [45.9-55.3]

• Note: Values in bold indicate statistical significance at the p<0.01 level.
• Source: Authors.

After adjusting for sociodemographic and behavioral variables, the odds for complete inactivity (zero min/week) of physical inactivity were 26% (OR 1.26; 95%CI: 1.06-1.51) higher in students with reporting feeling “always” isolated compared to those “never” isolated. Adolescents with “no friends” also had significantly higher odds of complete inactivity (OR: 1.69; 95%CI: 1.35-2.11) compared to those with “three or more friends”. In sex-stratified analyses, these associations remained significant among boys, especially for those who were always isolated (OR for 0 min/week: 1.71; 95%CI: 1.30-2.25), and among girls with limited social networks-girls with no friends had 1.53 times the odds of being completely inactive (95%CI: 1.07-2.18) compared to their more socially connected peers (Table 4).

Table 4
Unadjusted and adjusted odds ratios (95% confidence intervals) for different levels of physical inactivity, compared with ≥300 minutes/week of leisure-time physical activity, according to psychosocial characteristics among Brazilian schoolchildren.

Exposures		150 to 299 min/w OR[IC95%]	1 to 149 min/w OR[IC95%]	0 min/w OR[IC95%]
Total sample n=101,927
Social isolation - Ref. Never
Rarely	Unadjusted	1.34 [1.22-1.46]	1.16 [1.07-1.26]	1.23 [1.12-1.35]
	Adjusteda	1.26 [1.15-1.39]	1.02 [0.93-1.11]	1.02 [0.93-1.13]
Sometimes	Unadjusted	1.48 [1.34-1.64]	1.68 [1.54-1.82]	2.04 [1.87-2.23]
	Adjusteda	1.36 [1.22-1.51]	1.30 [1.19-1.42]	1.38 [1.25-1.52]
Most of time	Unadjusted	1.51 [1.29-1.76]	1.49 [1.32-1.69]	2.16 [1.89-2.47]
	Adjusteda	1.36 [1.17-1.59]	1.09 [0.96-1.24]	1.30 [1.13-1.49]
Always	Unadjusted	0.93 [0.76-1.14]	1.14 [0.96-1.35]	2.11 [1.80-2.49]
	Adjusteda	0.89 [0.73-1.09]	0.88 [0.74-1.06]	1.26 [1.06-1.51]
Social network - Ref. ≥3 friends
2 friends	Unadjusted	1.19 [1.06-1.34]	1.30 [1.18-1.44]	1.55 [1.41-1.71]
	Adjustedb	1.14 [1.00-1.31]	1.15 [1.03-1.29]	1.37 [1.21-1.54]
1 friend	Unadjusted	1.13 [0.93-1.38]	1.45 [1.23-1.70]	1.96 [1.66-2.31]
	Adjustedb	1.07 [0.86-1.32]	1.28 [1.06-1.54]	1.58 [1.32-1.89]
No friend	Unadjusted	0.85 [0.68-1.05]	1.13 [0.95-1.35]	1.44 [1.22-1.71]
	Adjustedb	0.94 [0.72-1.22]	1.27 [1.02-1.57]	1.69 [1.35-2.11]
Male n=49,218
Social isolation - Ref. Never
Rarely	Unadjusted	1.33 [1.19-1.49]	1.09 [0.98-1.21]	0.98 [0.87-1.10]
	Adjustedc	1.30 [1.16-1.46]	1.07 [0.97-1.20]	1.00 [0.89-1.12]
Sometimes	Unadjusted	1.42 [1.24-1.62]	1.42 [1.26-1.60]	1.38 [1.21-1.57]
	Adjustedc	1.40 [1.23-1.61]	1.37 [1.22-1.55]	1.31 [1.15-1.50]
Most of time	Unadjusted	1.59 [1.28-1.98]	1.38 [1.14-1.66]	1.79 [1.46-2.20]
	Adjustedc	1.59 [1.28-1.97]	1.35 [1.12-1.64]	1.70 [1.38-2.10]
Always	Unadjusted	0.76 [0.55-1.06]	0.99 [0.76-1.29]	1.85 [1.42-2.40]
	Adjustedc	0.81 [0.58-1.13]	1.02 [0.78-1.35]	1.71 [1.30-2.25]
Social network - Ref. ≥3 friends
2 friends	Unadjusted	1.27 [1.08-1.49]	1.30 [1.14-1.47]	1.35 [1.17-1.56]
	Adjustedd	1.21 [1.01-1.45]	1.23 [1.06-1.42]	1.31 [1.10-1.56]
1 friend	Unadjusted	1.20 [0.90-1.60]	1.41 [1.13-1.77]	1.98 [1.53-2.56]
	Adjustedd	1.23 [0.93-1.64]	1.38 [1.09-1.76]	1.75 [1.35-2.27]
No friend	Unadjusted	0.86 [0.65-1.13]	1.22 [0.97-1.53]	1.71 [1.39-2.11]
	Adjustedd	0.94 [0.68-1.31]	1.26 [0.95-1.68]	1.82 [1.37-2.41]
Female n=52,709
Social isolation - Ref. Never
Rarely	Unadjusted	1.15 [0.94-1.42]	0.91 [0.78-1.07]	0.98 [0.85-1.15]
	Adjustedc	1.14 [0.92-1.40]	0.90 [0.76-1.05]	0.97 [0.83-1.13]
Sometimes	Unadjusted	1.24 [1.03-1.50]	1.19 [1.04-1.37]	1.39 [1.21-1.61]
	Adjustedc	1.23 [1.02-1.48]	1.14 [0.99-1.31]	1.31 [1.13-1.51]
Most of time	Unadjusted	1.09 [0.87-1.36]	0.84 [0.70-0.99]	1.06 [0.90-1.25]
	Adjustedc	1.10 [0.88-1.37]	0.83 [0.69-0.98]	1.01 [0.85-1.19]
Always	Unadjusted	0.79 [0.60-1.05]	0.67 [0.54-0.83]	1.05 [0.86-1.28]
	Adjustedc	0.85 [0.64-1.13]	0.71 [0.56-0.88]	0.99 [0.81-1.23]
Social network - Ref. ≥3 friends
2 friends	Unadjusted	1.01 [0.83-1.22]	1.09 [0.94-1.27]	1.31 [1.13-1.51]
	Adjustedd	1.05 [0.84-1.31]	1.08 [0.90-1.29]	1.34 [1.12-1.60]
1 friend	Unadjusted	0.98 [0.73-1.31]	1.27 [1.01-1.59]	1.62 [1.28-2.04]
	Adjustedd	0.85 [0.60-1.21]	1.12 [0.87-1.46]	1.37 [1.06-1.77]
No friend	Unadjusted	0.93 [0.63-1.38]	1.25 [0.97-1.66]	1.61 [1.18-2.20]
	Adjustedd	0.91 [0.59-1.41]	1.22 [0.89-1.67]	1.53 [1.07-2.18]

• Notes: ^aAdjusted for sex, skin color, fruit & vegetable intake, alcohol consumption and drug use. ^bAdjusted for sex, age, maternal education, fruit & vegetable intake, alcohol consumption and drug use. ^cAdjusted for skin color, fruit & vegetable intake, tobacco and alcohol consumption. ^dAdjusted for age, maternal education, fruit & vegetable intake, alcohol and tobacco consumption. Bolded values are statistically significant (p<0.01).
• Source: Authors.

Discussion

This study aimed to investigate the association between social networks and social isolation with physical inactivity levels in Brazilian schoolchildren. The findings revealed that the majority of students were either physically inactive or insufficiently active, a concerning pattern that has been consistently reported in previous studies^1,22,27.

In the sex-stratified analysis, we observed significant differences in leisure-time physical inactivity levels, with girls being more inactive than boys, consistent with other research^7,28,29. These differences can be attributed to biological and sociocultural factors, particularly the gender roles assigned to boys and girls from a young age, which influence their engagement in physical activities. Girls are often encouraged to participate in lighter activities, based on the misconception about the fragility of their bodies and aesthetical concerns, whereas boys are typically urged to engage in more vigorous physical activities, due to the false perception of greater physical strength and capability³⁰.

A restricted social network was significantly associated with higher levels of physical inactivity. These results are consistent with other studies indicating that friends play a crucial role in supporting adolescents’ physical activity^{21,24,28,30-32}. A systematic review identified three key indicators of friendship that positively influence physical activity in children and adolescents: communication between friends about physical activity, role modeling and co-participation²³. Among Brazilian adolescents, the presence of friends was found to be the strongest association with physical activity³³.

Social isolation was linked with lower levels of physical activity only among male students. Previous studies in both high and middle-income countries have also reported an association between physical inactivity and feelings of loneliness in adolescents^20,34. Our results suggest that social network may be more influential than social isolation in this age group and population, highlighting the importance of peer relationships in adolescents’ physical activity. While loneliness can be a transient experience, friendships tend to be more enduring, providing sustained support to overcome the barriers to regular physical activity. In Brazilian students, higher levels of social support from parents and friends have been associated with greater self-efficacy in overcoming physical activity barriers³⁵. It could be hypothesized that the self-efficacy fostered by friends’ support may better help adolescents to cope with loneliness.

The pathways that explain the relationship between friendship networks and physical activity behavior can be explained by two models: peer contagion and peer selection. Peer contagion suggests that once individual become friends, their behaviors tend to align, particularly through social influence. Peer selection posits that individuals choose friends with similar interests, attitudes and behaviors³⁶. Qualitative studies have shown that young people seek physical activity primarily for enjoyment, and the presence of friends is a key motivator for this “fun” factor²³. Conversely, individuals with a limited social network, who have fewer friends, are likely to experience less social influence to engage in physical activity, and peer influence in general may also be weaker.

In the sex-stratified analyzes, the adjusted results indicate a relatively stronger effect of both social networks and social isolation on the physical inactivity levels of male students, suggesting that boys may be more influenced by their social networks compared to girls. These findings are consistent with a systematic review of 13 studies involving 24,997 children and adolescents, which showed that boys were more influenced by their friendships’ networks in terms of physical activity than girls¹⁶. This observation has been corroborated by studies on Brazilian adolescents, where the support of friends had a greater effect on boys’ physical activity than on girls’³⁵. Additionally, a cross-sectional study reported that self-efficacy, social norms, and community involvement in physical activity were important predictors of moderate-to-vigorous physical activity for boys; whereas for girls, only self-efficacy was a significant predictor³⁷.

Although the data analyzed in this study were collected prior to the COVID-19 pandemic, they remain relevant for understanding the association between social ties and leisure-time physical activity among adolescent students. First, the pandemic-related restrictions, such as school closures and social distancing, were temporary disruptions rather than long-term structural changes. As the transitory nature of these restrictions, it is plausible to assume that patterns of socialization and physical activity among adolescents are currently closer to the levels observed in the pre-pandemic period. Second, using pre-pandemic data allows for an examination of these associations under more normal social conditions, free from the confounding effects of emergency health policies and behavioral constraints. Thus, the data analyzed preserve relevance and validity and provides a valuable reference point for understanding the associations between social relationships and leisure-time physical activity in adolescent students.

Our study has limitations that should be acknowledged. Due to its cross-sectional nature, where outcomes and exposures were measured simultaneously, reverse causality cannot be ruled out. It could be argued that physical inactivity leads to a smaller network of friends and greater social isolation. For instance, using the same dataset, Werneck et al. ³⁸ found that physical activity was associated with lower prevalence of social isolation. Furthermore, our study utilized individual questions to measure the exposures, whereas well-established scales, such as the Social Support for Exercise Behavior Scale, the Survey of Children’s Social Support and the Adolescent Physical Activity Survey exist for assessing these constructs³⁹. We also did not evaluate family social support, can play a significant role in encouraging and sustaining physical activity in adolescents¹⁴. Additionally, our study relied on subjective measures of physical activity, which are less precise and accurate. Another limitation is the weekly aggregation physical activity time on a weekly basis, which fails to differentiate between consistent daily engagement and sporadic patterns concentrated over fewer days. Although the cutoff point of 300 minutes per week is consistent with international recommendations for additional health benefits, it does not capture adherence to the recommendation of 60 minutes of daily physical activity for teenagers. This may result in the misclassification of activity patterns and limit more sophisticated interpretations of behavioral routines associated with physical activity. Future research should employ longitudinal designs, validated scales for assessing exposures, and objective methods for measuring the outcome. However, our study’s strength lies in its large, nationally representative sample, which provides valuable insights into the relationships between social networks, social isolation and physical inactivity levels in adolescents.

In conclusion, a lower number of friends was associated with reduced levels of physical activity among adolescent students. Given the growing concern regarding insufficient levels of physical activity and its implications for the physical and mental health of adolescents, it is essential to understand the role of psychosocial factors, such as social support networks and peer influence, in promoting healthy behaviors. This understanding is vital for the development of effective public health interventions aimed at improving adolescent health and well-being.

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Data availability statement

The data sources adopted in the research are indicated in the article’s body.

Chief editors:

Maria Cecília de Souza Minayo, Romeu Gomes, Antônio Augusto Moura da Silva, Vania de Matos Fonseca

Publication Dates

• Publication in this collection
  09 Oct 2026
• Date of issue
  2026

History

• Received
  23 Aug 2024
• Accepted
  03 July 2025
• Published
  05 July 2025