Although the underlying mechanisms remain unclear, researchers have highlighted the impact of sleep patterns on myopia onset and progression, noting a later bedtime (9:30pm or later) is linked with an increased risk of myopia and myopia progression. They believe that the relationship may allude to a more complex relationship of indoor environment, activities, circadian rhythm and myopia.

The Shanghai study followed 6,295 children (ages six to 10) for 24 months using an app-based questionnaire completed by parents and caregivers four times a year. They found that children who went to sleep after 9:30pm were 1.55-times more likely to be diagnosed with myopia at baseline and 1.44-times more likely to have myopia by the two-year follow-up, after adjusting for residency area, age, sex and time spent outdoors (Table 1). Those who had the later bedtime were also more likely to experience myopia progression, the researchers noted. However, they found no evidence supporting a relationship between sleep duration and myopia.

The researchers suggest that sleeping late could be linked with more late-night near-based activities and more exposure to artificial lighting conditions. A child is highly likely to spend more time reading or being on digital devices while inside in the evenings. The team noticed that children who read more and spent more time on screens and less time outdoors were also more likely to go to bed later.

The researchers believe future studies on myopia should determine whether going to sleep late makes children more prone to myopigenic activities under poor lighting conditions when they are supposed to be sleeping or more susceptible to abnormal eye growth due to circadian disturbance.