BACKGROUND: Outdoor artificial light at night (ALAN) has emerged as a significant source of environmental pollution. However, epidemiological evidence on its impact on childhood myopia development remains limited. Therefore, this study aims to investigate the association between outdoor ALAN exposure and myopia development.
METHODS: This cross-sectional and prospective cohort study included children from the Hong Kong Children Eye Study, a population-based cohort with a 3-year follow-up. Outdoor ALAN exposure (nW/cm/sr) within 500 m of each residence was estimated using time-varying satellite data. Myopia was defined as cycloplegic spherical equivalent refraction ≤ -0.50 diopters. Associations were estimated using multivariable logistic regression and time-varying Cox proportional hazards models, adjusting for demographic (age and sex), behavioral (e.g., near-work and outdoor time), parental myopia, and socioeconomic (e.g., family income) factors. Restricted cubic splines were employed to explore exposure-response relationships. 2
RESULTS: A total of 19,114 children (mean [SD] age, 7.40 [1.10] years; 52.8% boys) were included at baseline, with 2,558 non-myopic children completing the prospective follow-up. In maximally adjusted models, each interquartile range increase in outdoor ALAN exposure was associated with an 8% higher risk of myopia prevalence (OR, 1.08; 95% CI, 1.02-1.15) and a 26% higher risk of myopia incidence (HR, 1.26; 95% CI, 1.16-1.37). Notably, restricted cubic splines indicated a non-linear relationship for myopia incidence (P for non-linearity = 0.007), with risk escalating sharply beyond 93.08 nW/cm/sr. Further subgroup analysis revealed that older children (≥ 7.35 years) were more vulnerable to outdoor ALAN-associated incident myopia (HR, 1.27; 95% CI, 1.17-1.39; P for interaction < 0.001) compared to younger children (< 7.35 years). 2
CONCLUSION: Outdoor ALAN exposure is positively associated with childhood myopia development. Given the observational design and limited understanding of mechanisms, further replication and mechanistic studies are warranted to confirm these findings to help inform future public health policies for myopia prevention.
