Do cell phones, iPods/MP3 players, siblings and friends matter? Predictors of child body mass in a U.S. Southern Border City Middle School.

Objective: This study examines the association of children's (i) micro-social environment, specifically siblings [kin-friends] and friends from school and neighborhood [non-kin-friends], and (ii) ownership of information and communication technologies (ICT), specifically cell phones and iPod/MP3 players, with body mass index percentile (BMIp).

Subjects: Fifty-five randomly selected 6th graders with a mean age of 12 years, stratified by gender (23 boys and 32 girls), from a Texas middle school located in a city along the U.S. southern border.

Methods: The linear regression of BMIp on number of siblings and of non-kin-friends, and ownership of cell phone and of iPod/MP3 player was examined using two models: M1 was based on the manual selection of predictors from a pool of potential predictors. M2 was derived from the predictors specified in M1 using backward elimination technique. Because sample size was small, the significance of regression coefficients was evaluated using robust standard errors to calculate t-values. Data for predictors were obtained through a survey. Height and weight were obtained through actual anthropometric measurements. BMIp was calculated using the on-line BMI calculator of the Center for Disease Control and Prevention.

Results: Findings reveal that children's social environment and ICT ownership predict BMIp; specifically, number of siblings (M2: β = -0.34, p-value < .001), and ownership of iPod/MP3 players (M2: β = 0.33, p-value < .001). These results underscore the importance of family in configuring, and of new personal technical devices (that encourage solitary, and oftentimes sedentary, activities) in predicting child body mass.