Research article
Physical Activity and Screen Time in Adolescents and Their Friends

https://doi.org/10.1016/j.amepre.2012.09.054Get rights and content

Background

Little is known about the actual physical activity and screen time behaviors of an adolescent's friends relative to the individual's behavior.

Purpose

To determine the associations between an adolescent's physical activity and screen time and his/her nominated friends' physical activity and screen time.

Methods

Data were obtained from EAT 2010 (Eating and Activity Among Teens), a large cross-sectional study (n=2126) conducted in 20 middle schools and high schools in Minneapolis/St. Paul MN during the 2009–2010 academic year and analyzed during 2011. Each participant nominated up to six friends from a school roster, and data from those friends were obtained as part of the school-based data collection procedures. Physical activity and screen time were assessed with previously used and validated questionnaires. Generalized estimating equation models, stratified by gender, were used to assess associations between adolescents' physical activity and screen time and their friends' physical activity and screen time.

Results

Physical activity for female adolescents was associated with their male and female friends' physical activity, including their male and female best friends (all p<0.05). Male adolescents' physical activity was associated with their female friends' physical activity (p<0.03). Female adolescents' screen time was associated with their male and female friends' screen time (p≤0.03), but not with that of their best friends. Male adolescents' screen time was associated with only their female friends' screen time (p=0.04).

Conclusions

The consistent association between female adolescents' physical activity and their friends' physical activity indicates a need to include peer effects on adolescent female physical activity in future intervention work.

Introduction

Physical activity levels suffer a marked decline during adolescence, especially for girls, with the most dramatic decline occurring between ages 15 and 18 years.1 Using longitudinal data from Project EAT (Eating and Activity among Teens), Nelson et al.2 reported significant declines (especially for girls/women) in moderate to vigorous physical activity (MVPA) in adolescents who were followed from age 16 years to age 20 years. This decline in MVPA is an important and timely issue, given currently low levels of adequate physical activity in youth,3 high levels of screen time,4 and recent increases in pediatric obesity and related chronic diseases.5, 6, 7, 8 There remains uncertainty, however, regarding the social factors associated with adolescent physical activity and screen time.

The social influences on adolescent physical activity primarily have been assessed by adolescents' perception of the social support they receive for being physically active from friends, family, and other adults who are important in their lives. Generally, perceived social support for physical activity is positively associated with higher physical activity in adolescents.9, 10, 11 However, some studies have found no association12, 13 or observed that the association is stronger for girls than boys.14 Although social support tells us about the supportive behaviors of friends, it does not tell us how active or inactive the friends are.

Even less is understood about the correlates and/or determinants of screen time or sedentary behavior in youth; only parent support for reduced screen time has been associated with child, but not adolescent, physical activity.15, 16, 17 A deeper understanding of social factors associated with adolescent physical activity and screen time behavior is warranted for several reasons. First, individuals become more autonomous from their parents and rely more heavily on behavioral cues from friends during adolescence.18, 19 Second, physical activity significantly declines during adolescence. Lastly, although peer social support for physical activity has been observed in previous studies, there is very limited research on the actual associations between peer and adolescent physical activity and screen time.

Using nominated-friend data represents a new approach to studying adolescents' social environments related to physical activity and screen time. Related to physical activity and screen time, a small number of studies20, 21, 22 using the National Longitudinal Study of Adolescent Health (Add Health) support the social causation spread of obesity in adolescents. The results, however, are not conclusive.23, 24 Even if obesity does indeed spread, to some extent, through social causation, researchers and health practitioners still need to understand the behaviors that directly contribute to that excess weight gain (e.g., physical activity and screen time for the current study). Therefore, focusing attention on the behavioral precursors of excess weight gain will provide more applicable information that can be used to develop obesity-prevention efforts.

Studies examining other behaviors such as substance use18, 25, 26, 27 have suggested a pattern of social causation but, to our knowledge, very limited research has been done with adolescent physical activity and screen time. There are only a limited number of studies that specifically investigated adolescent peer associations28, 29, 30, 31, 32 or influences33 on physical activity. Cross-sectional studies by Ali et al.28 using data from the Add Health study and by de la Haye et al.29 using data from 8th- and 9th-grade Australian students both observed associations between individual and peer physical activity.28, 29 Associations between individual and peer “other” screen time (not including TV/movies) also were reported.29 The association between individual and friend physical activity and screen time is especially relevant since time spent being physically active or in front of a screen can often involve social interactions with friends (e.g., sports teams, exercise partner, watching movies, or playing video games).

The Ali et al. study28 used a large nationally representative sample, but the analyses were not stratified by gender, limiting the interpretation of the results for future intervention development. The data in de la Haye et al.29 were stratified, and similar findings were observed across gender. Still, the sample was a relatively small sample (N=378) from Australia and did not include any older adolescents. A recent systematic review34 presents more-detailed information on research in this area.

The purpose of the current study was to examine whether friends' physical activity and screen time was related to an individual adolescent's (the “ego's”) physical activity and screen time by using data provided by nominated friends. The authors hypothesized that associations between ego and friend physical activity and screen time behavior would be significant between egos and friends of the same gender. In addition, it was hypothesized that because of increases in autonomy and greater reliance on behavioral cues from peers,18, 19 associations between ego and friend behaviors would be stronger for high school versus middle school students.

Section snippets

Sample

The EAT-2010 study was designed to examine dietary intake, physical activity, weight control behaviors, weight status, and factors associated with these outcomes in adolescents. Participants were adolescents (mean age 14.4±2.0 years) recruited from 20 public schools in Minneapolis and St. Paul MN. Six schools were traditional middle schools (6th–8th grade), eight were traditional high schools (9th–12th grade), three were kindergarten (K)–8th grade, one was K–12th grade, one was 6th–10th grade,

Results

Male adolescents reported more hours per week of MVPA than female adolescents (6.83±4.84 vs 4.98±4.40, p<0.001), but they also reported more hours per week of screen time (45.15±28.85 vs 36.51±23.92, p<0.001). MVPA among male adolescents was associated with MVPA of female friends (Table 2). On average, for every additional hour per week of female-friend MVPA, there were approximately six additional minutes of MVPA per week for male adolescents. MVPA in female adolescents was associated with the

Discussion

Several associations were observed between ego and friend MVPA and screen time, indicating that, to some extent, these behaviors are shared among friends. More associations were found among female adolescents for MVPA than among male adolescents, suggesting the importance of social relationships and social support for MVPA in female adolescents. The current study used the novel technique of ego-centric analysis to obtain data from the adolescents and the friends that they nominated, rather than

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    Meg Bruening was employed at the University of Minnesota when this research was completed.

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