Urban–rural disparities in menarcheal timing: a longitudinal cohort study examining social determinants of health (SDOH), screen time, and hormonal influences among adolescent girls in West Bengal, India

This study aimed to evaluate the association between early menarche, lifestyle factors, screen time (TV and mobile phones) and psychological factors among girls aged 8–10 years living in West Bengal, India, with special emphasis on hormonal and psychosocial influences and an urban-rural perspective using the Social Determinants of Health (SDOH) framework. A mixed-methods cohort study of 1,200 girls (600 urban, 600 rural) was followed up over three years. Quantitative (hormone assays, anthropometrics) and qualitative (body image, screen use interviews) approaches were used to measure screen time, physical activity, sleep, diet, hormone levels (melatonin, cortisol, GnRH, LH, FSH, estradiol, leptin), anthropometrics (BMI, Tanner staging), and psychological outcomes (stress, anxiety, self-perception). Urban girls with > 4 h/day of screen time had ≈ 4.2 months earlier menarche onset than rural girls with < 2 h/day. In urban girls, early menarche was linked to increased cortisol, decreased melatonin, and increased estradiol, associated with greater sedentary activity and stress from social media. Rural girls exhibited resilience amid family stress. Urban girls had body image issues; rural girls used screens as a means of escape. Excessive screen time, hormonal interference, and growth accelerators, from increasingly worse urban diets to the exacerbation of inactivity and presenteeism, help explain the acceleration, which affects urban girls especially, given the activity-inactivity model & the potential for online bullying associated with a reliance on social media. Qualitative data elucidate the protective resilience of rural girls, constructing urban body dissatisfaction, rural escape mobility, and environmental contexts. Our findings concluded that screen exposure accelerates menarche through psychobiological mechanisms, especially significant in urban-rural differences. To mitigate screen time effects and protect girls’ health across settings, context-specific interventions are critical. The SDOH framework highlighted how structural factors-like digital access, education stress, and community dynamics-shape puberty in meaningful ways.