Outdoor Light at Night and Children's Body Mass

Background: Emerging evidence supports an association between light at night (LAN) exposure with obesity or overweight in adults. However, effects of LAN exposure during childhood have yet to be further investigated.

Objective: In this study, we aimed to determine whether LAN exposure is associated with body mass in young children.

Research design and method: We used data from the Fr1da cohort study which screened children for early-stage islet autoimmunity in Bavaria, Germany from February 2015 to March 2019. A total of 62,212 children aged <11 years with complete residential information was included in the analysis. Self-reported weight and height were used to calculate age- and sex-specific body mass index (BMI) z-scores. LAN exposure was based on remotely sensed images from Visible Infrared Imaging Radiometer Suite and assigned to the children's residencies. We used generalized additive models to estimate the associations between LAN exposure and BMI adjusting for potential confounders.

Results: We observed an increase in BMI z-scores of 34.0% (95% confidence interval (CI): 25.4-42.6) per 10 nW/cm2/sr increment in LAN exposure at baseline (2015) and of 32.6% (24.3-41.0) for LAN exposure one year prior to screening, both adjusted for age and sex. Similar associations were observed after adjustment for socioeconomic status and urbanization degree.

Conclusion: Our findings suggest that outdoor light exposure may be a risk factor for weight gain during childhood.