Joint association of screen time and physical activity with anthropometric measures in Iranian children and adolescents: the weight disorders survey of the CASPIAN-IV study

Abstract

Background: This study aims to assess the joint association of screen time (ST) and physical activity (PA) with anthropometric indices among Iranian children and adolescents. Methods: In this national study, 23,183 school students, aged 6-18 years, were studied. By using a multi-stage cluster sampling method, they were selected from rural and urban areas of 30 provinces of Iran. ST and PA were assessed by self-administered validated questionnaires. Height, weight, hip and waist circumferences (WC) were measured according to standard protocols, and body mass index (BMI) was calculated. ST of <2 h per day was categorized as "low" and >= 2 h per day as "high". PA levels were obtained by a 7-day recall of sports or activities that made participants sweat or make their legs feel tired, or games that made them breathe heavily. Using this questionnaire, the score of 1-1.9 was categorized as "low" and scores between 2 and 5 as "high" PA. Logistic regression analyses were used to evaluate the joint association of PA and ST categories with odds of anthropometric measures. Results: In both genders, those students categorized as "Low PA & High ST" had the highest levels of BMI z-scores (boys: 0.15 +/- 1.12, girls: 0.17 +/- 1.08), WC (boys: 69.93 +/- 13.89 cm, girls: 67.30 +/- 11.26 cm), and hip circumference (boys: 82.41 +/- 13.90 cm, girls: 84.05 +/- 13.7 cm), as well as the highest prevalence of overweight (boys: 15.32, girls: 14.04) (p < 0.001 in all comparisons). In linear multivariate model, students with "High PA & High ST" had significant increased levels of z-scores for BMI, WC and hip circumference (p < 0.05). Conclusions: The current findings underscore the importance of reducing ST along with increasing PA for prevention and control of excess weight in children and adolescents.