Predictability of TV Viewing Throughout Childhood: Iowa Bone Development Study

Abstract

PURPOSE: Tracking studies determine the stability and predictability of specific phenomena. This study examined tracking of TV viewing (TV) from middle childhood through early adolescence after adjusting for moderate and vigorous physical activity (MVPA), percentage of body fat (% BF), and maturity. METHODS: TV was measured at ages 5, 8, 11, and 13 yr (n = 434) via parental- and self-report in a population-based cohort. MVPA was measured using the Actigraph, % BF using dual-energy x-ray absorptiometry, and maturity via Mirwald predictive equations. Generalized Estimating Equations (GEE) were used to assess stability and logistic regression was used to predict children "at risk" for maintaining excessive TV (> 2 hr). Additional models examined tracking in overfat children (boys ≥ 25% BF; girls ≥ 32% BF combined). RESULTS: More than half of the sample reported more than 2 hrs of TV daily at each measurement age. The crude GEE coefficients were 0.35 (95% CI = 0.26, 0.44) for boys, 0.34 (0.26, 0.43) for girls, and 0.41 (0.23, 0.59) for overfat. The GEE, adjusted for MVPA, % BF, and maturity, were 0.35 (0.26, 0.44) for boys and 0.32 (0.23, 0.40) for girls. The GEE, adjusted for MVPA, maturity, and gender, in the overfat (boys and girls combined) was 0.45 (0.27, 0.64). Gender (being female) was significant in this model. The adjusted OR were 3.2 (2.0, 5.2) for boys, 2.9 (1.9, 4.6) for girls, and 6.2 (2.2, 17.2) for overfat. That is, boys and girls were 3 times as likely to watch excessive TV later in life if they were excessive TV watchers at age 5 yr. For those overfat at age 5 yr (especially girls), the odds were much higher (6 times as likely). CONCLUSION: TV is moderately stable throughout childhood and predictive of later viewing behavior. It appears to be entrenched in younger children, especially overfat, young girls. Adjusting for MVPA did not significantly alter results suggesting that PA and sedentarism are distinct behaviors. Since habitual patterns of excessive TV in young children tended to continue into adolescence, tailored, early intervention strategies may be warranted to prevent excessive TV before it begins. Supported by the National Institute of Dental and Craniofacial Research (R01-DE12101, R01-DE09551); General Clinical Research Centers Program (M01-RR00059); National Center for Research Resources (UL1 RR024979).