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

Abstract

We sought to assess the effects of exposure to secondhand smoke (SHS) on peripapillary retinal nerve fiber layer (p-RNFL) thickness in children. Cross-sectional study. 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. 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 4.4μm (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). 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.