Smartphone use health outcomes in children and adolescents: A systematic review of behavioral, developmental, and environmental risk pathways

Table 9 Summary of studies examining smartphone use, physical activity, and childhood obesity (by age and study design)

Ref.	Country	Age group	Design	Sample size	Exposure definition	Physical activity outcome	Obesity outcome	Primary bias considerations	Risk of bias (JBI)
Byun et al[74], 2024	Korea	4th and 7th grade (approximately 10-13 years)	Cross-sectional	5180	Smartphone ≥ 180 minutes/day vs < 60 minutes/day	Isotemporal substitution: Replacing 1 hour screen with PA reduced obesity odds (OR = 0.75)	OR = 2.75 (95%CI: 2.06-3.68) for ≥ 180 minutes/day	Large sample size; however, height, weight, and screen time were all self-reported by adolescents	Moderate
Li et al[75], 2025	Korea	Adolescents (approximately 12-18 years)	Cross-sectional (national survey)	50407	≥ 6 hours weekend smartphone use	Sedentary time ≥ 6 hours ↑ obesity risk; MSE protective (OR = 0.45 males)	Females: OR = 1.57 for ≥ 6 hours weekend smartphone use	Robust national dataset with high power; adjusted for multiple socioeconomic confounders	Low
Ma et al[76], 2021	China (Shanghai)	Primary-high school	Cross-sectional	8419	Problematic smartphone use (entertainment)	Not primary focus	OR ≈ 1.03 per unit PSU score; stronger in females	Large multi-school sample; obesity status derived from objective school health records	Low to moderate
Yaakoubi et al[77], 2026	Tunisia	14-16 years	Cross-sectional	960	Problematic smartphone use (SAS-SV)	Vigorous PA markedly reduced in PSU group	Obesity 12.6% vs 0.7% in non-PSU	High accuracy in exposure via device tracking features; moderate RoB due to cross-sectional nature	Low to moderate
Raustorp et al[78], 2015	Sweden	8-9 years and 11-12 years	Repeated cross-sectional (2000-2013)	397 total cohorts	Era comparison (smartphone uptake period)	24% decline in steps/day (11-12 years boys)	BMI stable over time	Used objective pedometers; however, utilized a convenience sample with smaller cohort sizes in later years	Moderate

Risk of Bias assessment has been performed using the Joanna Briggs Institute checklist for analytical cross-sectional studies and ergonomic assessments. JBI: Joanna Briggs Institute; PA: Physical activity; OR: Odds ratio; CI: Confidence interval; PSU: Problematic smartphone use; SAS-SV: Smartphone Addiction Scale-Short Version; RoB: Risk of Bias; BMI: Body mass index.