Smartphone addiction among adolescents: associations with mental health, physical inactivity, daytime sleepiness, and consumption of ultra-processed foods.

OBJECTIVE: To estimate the prevalence of smartphone addiction and identify associated factors among high school adolescents. METHODS: A cross-sectional study, part of the first phase of the project "Longitudinal Study on Adolescent Behavior in Physical Activity and Health," was conducted with 1,616 adolescents of both sexes from public schools in Montes Claros, Minas Gerais, Brazil. Sociodemographic data, lifestyle habits, health aspects, and future expectations were collected. Smartphone addiction was assessed using the Smartphone Addiction Inventory (SPAI) with a cutoff score of ≥9. Additionally, levels ofphysical activity, eating habits, daytime sleepiness, depressive and anxious symptoms, presence of pain, weight satisfaction, body mass index, waist-to-height ratio, and future perspectives were evaluated. Prevalence ratios (PR) with 95% confidence intervals (95%CI) were estimated using Poisson regression with robust variance in both crude and adjusted analyses (p<0.05). RESULTS: The prevalence of smartphone addiction was 54.9%. Associated factors included female sex (PR 1.15; 95%CI 1.00-1.20), not practicing of physical activity (PR 1.10; 95%CI 1.00-1.22), consumption of salty industrialized/ultra-processed foods (PR 1.16; 95%CI 1.05-1.28) and fast foods (PR 1.16; 95%CI 1.04-1.28), presence of daytime sleepiness (PR 1.65; 95%CI 1.39-1.95), symptoms of depression (PR 1.42; 95%CI 1.22-1.65), and stress (PR 1.27; 95%CI 1.11-1.45). CONCLUSIONS: More than half of the adolescents demonstrated smartphone addiction, which was associated with female sex, unhealthy eating habits, and unfavorable emotional indicators. The findings highlight the importance of interventions that promote healthy behaviors and provide psychological support for this population.