Sex Moderates the Associations Between Perceptions of the Physical and Social Environment with Physical Activity in Youth

Background and Purpose Youth across the United States are insufficiently active. Emerging literature has identified numerous perceived correlates of physical activity in youth but many studies rely on associations with self-reported physical activity. However, a recent review of studies utilizing perceived environmental correlates and objectively-measured physical activity in youth concluded that inconsistent results were observed across studies (Ding, Sallis, Kerr, Lee, & Rosenberg, 2011). Furthermore, preliminary evidence suggests the relationship between physical and social environment correlates and physical activity in youth may differ between boys and girls. For example, Wenthe and colleagues (Wenthe, Janz, & Levy, 2009) found differences by sex in the association between access to facilities and moderate to vigorous physical activity (MVPA) among a sample of adolescent youth with only males displaying a positive association.

Objectives The objective of the present study was to determine if the relationships between perceptions of individual and aggregate physical/social environment measures and MVPA were moderated by sex in a large sample of 4th – 8th grade youth from North Carolina.

Methods Youth from 18 counties in North Carolina were recruited to participate in baseline data collection as part of a larger study examining the effects of community-based mini-grants on physical activity in youth. Survey items consisted of eight questions which asked about the presence or absence of physical and social factors (e.g., safety, sidewalks, social support) previously identified to be associated with physical activity in youth (Evenson, Scott, Cohen, & Voorhees, 2007). Youth were asked to wear accelerometers (ActiGraph, Pensacola, FL) for seven days, removing the monitors when bathing and sleeping. Days were considered complete if at least 10 valid hours were present for analysis. Daily MVPA was calculated by summing minutes of moderate and vigorous PA from valid days utilizing previously established cut-points (Evenson, Catellier, Gill, Ondrak, & McMurray, 2006). For the present study, only data from youth who provided complete questionnaire data on the items of interest and four valid days of accelerometer data were included (n=824, 71%). For each of the eight items and a summary environmental perception variable (i.e., number of ―yes‖ responses; range 0 to 8) two nested, multilevel linear regression models were employed. MVPA was first regressed onto sex and environmental perception items while controlling for grade and race. The interaction term between sex and environmental perception was then added to the model. The models adjusted for clustering at the county and individual level. All analyses were conducted in STATA 12.1.

Results Results of the unconditional multilevel models indicated the mean MVPA was 38.8 minutes/day for males and 27.8 minutes/day for females. County of residence accounted for 5.9% of the variance in MVPA. A significant positive association was observed in the first models (which did not include the interaction term) between MVPA and three items; ―I often see other girls or boys playing outdoors in my neighborhood,‖ ―My parents (or guardian) allow me to walk in our neighborhood on my own,‖ and ―My parents (or guardian) allow me to bike in our neighborhood on my own.‖ These effects were fully moderated by sex, with males who indicated ―yes‖ on these items exhibiting 4.4 – 5.3 more minutes of MVPA than males who indicated ―no‖ (Table 1). Results of the final model that examined the relationship between the environmental perceptions summed score indicated that being male was associated with 3.5 additional minutes of MVPA compared to females. The relationship between the environmental perceptions summed score and MVPA was completely moderated by sex, as each additional ―yes‖ response was associated with 1.5 additional minutes of MVPA for males.

Conclusions In the current sample, environmental perceptions appear to be related to MVPA, but this relationship is only present in males. Future research to elucidate these findings should be conducted to identify modifiable social and physical characteristics that are associated with MVPA in females.

Support/Funding Source This work was supported by a grant from the Active Living Research program of the Robert Wood Johnson Foundation. Additional support was provided in-kind by the North Carolina Department of Health and Human Services.