This study aimed to explore the association between screen exposure in early life and preschool myopia. During the baseline survey of the Longhua Child Cohort Study (LCCS), data of 29,595 preschoolers were collected via a caregiver-reported questionnaire regarding children’s socio-demographic characteristics, visual status, screen exposure and relevant parental information. Data of 26,433 preschoolers with normal eyesight or myopia were included in the analysis and cox regression modelling was employed to assess the associations. Results suggested the hypothesis that screen exposure in early life could be significantly and positively associated with preschool myopia, and in agreement with this hypothesis was the association being strengthened with the increasing daily exposure duration and total years of exposure; in the stratification analysis based on the presence of parental myopia, these associations still existed, and the strength of associations was stronger in preschoolers with myopic parents than those without. Moreover, a statistically significant association was only observed between initial screen exposure that occurred during 0–1-years old and myopia for preschoolers without myopic parents, while the significant associations were observed between initial screen exposure that occurred during 0–1, 1–2, 2–3, and after 3 years old and myopia for preschoolers who had myopic parents, with the strongest association found in the group of children initially exposed to electronic screens during 0–1 year old. Thus our findings indicated the hypothesis that screen exposure in early life might be associated with the occurrence of preschool myopia, and that the postnatal first year might be the sensitive period for the association. However, it is premature to conclude that early screen time leads to myopia with current data. Further longitudinal studies performed with cycloplegia are necessary to verify the hypothesis and shed light on the more urgent question whether early screen exposure contributes to the later myopia epidemic of school-aged children.

Screen media usage has become increasingly prevalent in daily life with children being exposed to screens at an early age. This is a growing public health concern with evidence linking screen exposure to detrimental health outcomes, whereas relationship between screen exposure and the presence of astigmatism among preschoolers remains unknown, thus we aimed to resolve this issue. During the 2017 survey of the Longhua Child Cohort Study, data of 29,595 preschoolers were collected via a caregiver-reported questionnaire regarding socio-demographics, screen exposure and refraction. Cox regression models were adopted to generate adjusted prevalence ratios (APR) and 95% confidence intervals (CI) to estimate the association between early screen exposure and astigmatism. 28,029 preschoolers were included in the final analysis. After adjustment for potential confounders, screen exposure during early life was significantly associated with the increased risk of astigmatism (APR and 95% CI: 2.25, 1.76–2.88), and the greatest risk was observed in the period from birth to 1-year (APR and 95% CI: 3.10, 2.41–3.98). The risk of astigmatism increased with both the total years of exposure and the average daily duration of screen exposure. Our findings suggested that preschoolers who were exposed to screens during early life might have an increased risk of astigmatism.

Exposure to prenatal maternal stress (PNMS) has been implicated as a risk factor for a range of psychiatric disorders in children. However, there have been a few studies showing inconsistent associations between PNMS and offspring autistic‐like behaviours. We therefore aimed to examine whether trimester‐specific PNMS exposure might be related to an increased risk of autistic‐like behaviours among preschoolers. Using data from Longhua Children Cohort Study, mothers of 65,931 preschool children were asked to recall their level of PNMS in each of the three trimesters of pregnancy, while children's current autistic‐like behaviours were assessed using the Autism Behaviour Checklist. A series of Cox regression models were fitted to assess the association between PNMS exposure and autistic‐like behaviours. After adjusting for potential confounders, the Cox regression models showed that PNMS exposure, especially during the second pregnant trimester, was significantly and positively associated with the presence of children's autistic‐like behaviours. The strength of these associations was enhanced with the increase of PNMS exposure level. Furthermore, based on different permutations of exposure versus no exposure in each trimester, the participants were divided into eight groups. A cross‐over analysis confirmed the aforementioned finding that the second pregnant trimester might be the sensitive period for PNMS exposure increasing the risk of autistic‐like behaviours. Our findings supported the hypothesis of an association between PNMS exposure and autistic‐like behaviours among preschoolers. Preventive interventions should be trialled to examine whether minimizing maternal psychological stress during pregnancy, especially the second trimester, may reduce the risk of offspring autistic‐like behaviours.