Children who live in areas with greater outdoor artificial light at night (ALAN) are more likely to have myopia, and more likely to develop it, according to a large population-based study out of Hong Kong that adds nighttime light pollution to the list of factors potentially influencing refractive development in children.
The research, published in Environmental Research,1 drew on data from 19,114 children enrolled in the Hong Kong Children Eye Study, a population-based cohort with a three-year follow-up. At baseline, participants had a mean age of 7.40 years and 52.8% were boys. Within that group, researchers followed a prospective cohort of 2,558 children who did not have myopia at baseline, tracking who went on to develop the condition over the following three years. Myopia was defined as a cycloplegic spherical equivalent refraction of −0.50 dioptres or worse.
Rather than relying on self-reported exposure, the investigators used satellite-derived measurements of nighttime light within a 500-metre radius of each child’s home, then linked this to cycloplegic refraction results.
for every interquartile increase in outdoor ALAN exposure, children had an 8% higher likelihood of already having myopia, and a 26% higher risk of developing it during the follow-up period
Key Findings
The study found that for every interquartile increase in outdoor ALAN exposure, children had an 8% higher likelihood of already having myopia, and a 26% higher risk of developing it during the follow-up period. Children in the highest quartile of exposure had a 34% greater risk of incident myopia than those in the lowest quartile.
These figures come from multivariable logistic regression and time-varying Cox proportional hazards models, and held up even after the researchers adjusted for a range of known risk factors, including age, sex, baseline refraction, time spent outdoors, near-work habits, parental myopia, socioeconomic background (such as family income), sleep duration, indoor bedroom lighting, access to greenspace and air pollution.
Not A Straight Line
Rather than a steady, linear increase in risk, the relationship between light exposure and myopia followed a more complex pattern. For new cases of myopia, risk stayed relatively flat until outdoor ALAN exposure reached 93.08 nW/cm²/sr, beyond which the risk climbed sharply, a nonlinearity the authors describe as statistically significant (P=0.007). For existing myopia, the steepest rise in risk occurred at lower levels of exposure, before levelling off as exposure increased further.
Age also played a role. Children aged 7.35 years and older were significantly more vulnerable to ALAN-associated incident myopia than younger children (P for interaction <0.001). The authors suggest this may reflect older children going to bed later due to heavier academic workloads, combined with a life stage in which the eye is growing more rapidly.
Possible Mechanisms
The authors point to several biologically plausible explanations. Outdoor light at night may suppress melatonin production and disturb circadian rhythms by activating light-sensitive retinal ganglion cells, an effect thought to be more pronounced with LED lighting given its high proportion of short-wavelength blue light. Disrupted circadian rhythms have previously been linked to abnormal patterns of axial elongation and eye growth in animal studies. The researchers also raise the possibility that the wavelength of light itself, separate from its timing, may affect eye growth through retinal signalling and chromatic aberration.
Limitations Acknowledged
The authors are careful to frame their findings as an association rather than proof of cause and effect. They note that satellite-based measures of outdoor light could not capture indoor lighting, screen use, blackout curtains or sleep masks, meaning individual exposure may have been imprecisely estimated. Only around 18% of the initially non-myopic children completed the full three-year follow-up, and the study population was drawn from Chinese children in Hong Kong, which may limit how well the findings apply elsewhere.
They concluded that more work, including studies using objective personal light-monitoring devices and further mechanistic research, is needed before nighttime lighting can be considered a genuine target for myopia prevention efforts or factored into urban planning policy.
Reference
- Li Y, Zhang Y, Kam KW, et al. Outdoor artificial light at night exposure and risk of myopia: a cross-sectional and prospective cohort study among Hong Kong children. Environ Res. 2026;303:124647.
