[Association between light exposure at night and pubertal development in children and adolescents]

Objective: To investigate the association between indoor light exposure at night and pubertal development in children and adolescents, and evaluate whether these associations differ by exposure window (1 hour before sleep, 1 hour after sleep, and 1 hour before waking) and sex. Methods: Data were collected from the baseline survey and 1-year follow-up of the "Intervention Study of Comorbidity of Myopia and Obesity in Children and Adolescents in Beijing". A total of 671 students aged 6-14 years were included. Bedroom light exposure levels at night were measured within 1 hour before sleep, 1 hour after sleep and 1 hour before waking by using portable illuminometers for four consecutive nights from 2022 to 2023. Pubertal development was assessed by parent-reported Tanner stages, with onset defined as Tanner stage ≥Ⅱ and progression as an increase in Tanner stage at follow-up. Logistic regression models were applied, adjusting for age, sex, school, BMI, only-child status, sleep duration and diet quality. Results: Overall, the light exposure at night 1 hour before waking was inversely associated with pubertal onset at baseline survey. Compared with the reference group (≤3.00 lx), the ORs for the overall 3.01-10.00 lx and >30.00 lx groups were 0.18 (95%CI: 0.07-0.50) and 0.22 (95%CI: 0.07-0.72), respectively. Each log-unit increase in overall light exposure at night 1 hour before and 1 hour after sleep was associated with increased risk of pubertal progression by 18% (OR=1.18, 95%CI: 1.04-1.33) and 14% (OR=1.14, 95%CI: 1.02-1.28), respectively. In subgroup analyses, among boys, each 1-log-unit increase in nighttime light exposure 1 hour before waking was associated with an 18% (OR=0.82, 95%CI: 0.70-0.96) lower risk of pubertal onset , while each 1-log-unit increase in nighttime light exposure 1 hour before sleep and 1 hour after sleep was associated with 22% (OR=1.22, 95%CI: 1.04-1.43) and 17% (OR=1.17, 95%CI: 1.02-1.35) higher risks of pubertal progression, respectively. Among girls, each 1-log-unit increase in nighttime light exposure 1 hour before waking was associated with a 17% (OR=0.83, 95%CI: 0.71-0.98) lower risk of pubertal progression. Conclusions: Bedroom nighttime light exposure before and after sleep may promote pubertal progression in children and adolescents, whereas nighttime light exposure before waking may delay pubertal onset, and these associations differed by sex. Greater attention should be paid to promoting a healthy nighttime light environment for children and adolescents in sexual health education.