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Original Investigation
October 17, 2019

Association of Secondhand Smoking Exposure With Choroidal Thinning in Children Aged 6 to 8 Years: The Hong Kong Children Eye Study

Author Affiliations
  • 1Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong
  • 2Department of Ophthalmology, Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine, Hangzhou, China
  • 3Department of Ophthalmology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian, China
  • 4Hong Kong Eye Hospital, Hong Kong
  • 5Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong
JAMA Ophthalmol. Published online October 17, 2019. doi:https://doi.org/10.1001/jamaophthalmol.2019.4178
Key Points

Question  Is there an association between secondhand smoking and choroidal thickness in children?

Findings  In this cross-sectional study of 1400 Hong Kong children, choroidal thickness was associated with the number of smokers and quantity of smoking in the family.

Meaning  The data provide information to suggest that exposure to secondhand smoking in children is associated with choroidal thinning along a dose-dependent effect; avoidance of cigarette smoking in living environments of children should be advocated.

Abstract

Importance  Secondhand smoking is a risk to adult ocular health, but its effect on children’s ocular development is not known.

Objective  To assess the association between choroidal thickness and secondhand smoking exposure in children.

Design, Setting, and Participants  Children aged 6 to 8 years were consecutively recruited from January 2016 to July 2017 from the population-based Hong Kong Children Eye Study at the Chinese University of Hong Kong Eye Centre. All participants underwent detailed ophthalmic investigations. Choroidal thickness was measured by swept-source optical coherence tomography, with built-in software that automatically segmented the choroid layer to analyze its terrain imagery. History of secondhand smoking was obtained from a questionnaire. Multiple linear regression analyses were performed to assess the correlation between choroidal thickness and secondhand exposure when controlling for confounding factors. Analysis began July 2018 and ended in April 2019.

Main Outcomes and Measurements  The association between children’s choroidal thickness and their exposure to secondhand smoking.

Results  Of 1400 children, 941 (67.2%) had no exposure to secondhand smoking, and 459 (32.8%) had exposure to secondhand smoking. The mean (SD) age was 7.65 (1.09) years for children in the nonexposure group and 7.54 (1.11) years for children in the exposure group. After adjustment for age, sex, body mass index, axial length, and birth weight, exposure to secondhand smoking was associated with a thinner choroid by 8.3 μm in the central subfield, 7.2 μm in the inner inferior, 6.4 μm in the outer inferior, 6.4 μm in the inner temporal, and 7.3 μm in the outer temporal. Choroidal thinning with also associated with increased number of family smokers and increased quantity of secondhand smoking. An increase of 1 family smoker was associated with choroidal thinning by 7.86 μm in the central subfield, 4.51 μm in the outer superior, 6.23 μm in the inner inferior, 5.59 μm in the outer inferior, 6.06 μm in the inner nasal, and 6.55 μm in the outer nasal. An increase of exposure to 1 secondhand cigarette smoke per day was associated with choroidal thinning by 0.54 μm in the central subfield, 0.42 μm in the inner temporal, and 0.47 μm in the outer temporal.

Conclusions and Relevance  This investigation showed that exposure to secondhand smoking in children was associated with choroidal thinning along with a dose-dependent effect. These results support evidence regarding the potential hazards of secondhand smoking to children.

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