Abstract
OBJECTIVE: Despite growing concerns regarding the impact of smartphone use on adolescents' lifestyle, there is a notable lack of studies utilising national data to explore how smartphone use influences eating habits in this age group. We aimed to investigate the association between smartphone screen time and fast food intake using representative data from Korean adolescents. DESIGN: Cross-sectional survey. SETTING: This cross-sectional analysis used data from the 2017 Korean Youth Risk Behavior Web-based Survey (KYRBS). We used Poisson regression to directly estimate prevalence ratios (PRs) rather than using logistic regression as odds ratios (ORs) tend to overestimate PRs when the outcome is common. Smartphone screen time was categorised into four groups based on the daily time spent using smartphones: <2 hours/day, 2-3 hours/day, 4-5 hours/day and ≥6 hours/day. Fast food intake was assessed based on the weekly intake frequency of pizza, hamburgers, fried chicken and carbonated beverages (infrequent consumption: ≤2 times/week; frequent consumption: ≥3 times/week). PARTICIPANTS: Data from 39 753 individuals were included. PRIMARY OUTCOME MEASURES: The primary outcome was the frequency of fast food intake, assessed via a self-reported survey that asked: "In the past 7 days, how often did you eat fast food such as pizza, hamburgers, fried chicken, or drink carbonated beverages?". Participants were categorised into two groups based on their median intake: infrequent (≤2 times/week) and frequent (≥3 times/week). RESULTS: Among 39 753 adolescents, 19 273 reported frequent fast food intake (10 162 (51.9%) boys, 9111 (45.1%) girls), while 20 480 reported infrequent intake (9409 (48.1%) boys, 11 071 (54.9%) girls). The probabilities that adolescents who used smartphones for 6 hours daily would have frequent fast food intake were 1.29 times (95% CI: 1.28 to 1.30) among boys, and 1.43 times (95% CI: 1.42 to 1.44) higher among girls, compared with adolescents who used smartphones for 2 hours daily. CONCLUSION: The association between prolonged smartphone screen time and frequent fast food intake in adolescents suggests the need for targeted interventions addressing digital media use to promote healthier eating behaviors.