Original Article
Exposure to Secondhand Smoke in Children is Associated with a Thinner Retinal Nerve Fiber Layer: The Hong Kong Children Eye Study

https://doi.org/10.1016/j.ajo.2020.10.016Get rights and content

Highlights

  • •

    Children exposed to secondhand smoke had a thinner peripapillary retinal nerve fiber layer.

  • •

    As the optic nerve, quantified by retinal nerve fiber layer thickness, is part of the central nervous system, exposure tosecond hand smoke could lead to neurodevelopmental deficits.

  • •

    It is recommended that children avoid exposure to cigarette smoke in living environments.

Purpose

We sought to assess the effects of exposure to secondhand smoke (SHS) on peripapillary retinal nerve fiber layer (p-RNFL) thickness in children.

Design

Cross-sectional study.

Methods

Children 6-8 years of age were consecutively recruited from the population-based Hong Kong Children Eye Study. All participants received comprehensive ophthalmic examinations and p-RNFL thickness was measured by spectral-domain optical coherence tomography. SHS data were derived from a validated questionnaire. Associations between p-RNFL thickness and SHS exposure status, number of smokers in the family, and quantity of smoking in the family were determined by multivariate linear regression after adjusting for potential confounders.

Results

Among the Hong Kong Children Eye Study cohort (n = 3,103), approximately one-third of children were exposed to SHS (35.4%, n = 1,097). Compared to those without exposure to SHS, children exposed to SHS had similar age (P = .83), gender (P = .17), body mass index (P = .44), birth weight (P = .23), and axial length (P = .34), but had lower family income (P < .001) and lower parental education level (P < .001). After adjusting for all the above factors, exposure to SHS was associated with a thinner global p-RNFL by 4.4 μm (P < .001). Reduced p-RNFL was also associated with increased numbers of smokers in the family (β = −3.40, P < .001) and increased quantity of SHS (β = −0.22, P < .001).

Conclusions

Exposure to SHS in children was associated with a thinner p-RNFL. A thinner p-RNFL may increase the risk of irreversible visual impairment in the future. Our results provide evidence to recommend that children avoid exposure to SHS.

Section snippets

Study Population

Primary school children from grades 1-3 (approximately 6-8 years of age) were recruited from the ongoing HKCES, which has been described previously.21, 22, 23 In brief, the HKCES was designed to determine the occurrence and development of childhood eye diseases, including refractive errors, strabismus, amblyopia, and allergic eye diseases, and to identify the environmental and genetic determinants of these ocular disorders. Sample selection was based on a stratified and clustered randomized

Characteristics of the Study Population

A total of 3,416 Chinese children underwent ophthalmic investigations, but 286 children were excluded because of poor-quality OCT images. Twenty-seven children were further excluded because of incomplete ophthalmic examinations, leaving 3,103 children in the final analysis. The demographic data are presented in Supplemental Table 2. There were 133 families with ≥1 child joined the HKCES, and only 1 of them from each family was randomly recruited. Among the study subjects, 1,097 (35.4%) had

Discussion

To the best of our knowledge, this study is the one of the first to report that early exposure to SHS is associated with thinner p-RNFL in children. The findings show that children 6-8 years of age who were exposed to SHS had a thinner p-RNFL after adjusting for age, gender, BMI, AL, birth weight, outdoor activity time, reading distance, family income, and parents' education level. Our study provides further evidence to support the recommendation that the public should avoid smoking around

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    • Cited by (0)

    Supplemental Material available at AJO.com.

    1

    Drs Li and Yuan served jointly as first authors.

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