Secondhand smoking potentially harmful to eye health of kids : JAMA

Hong Kong: Secondhand smoking may have a potentially harmful impact on children's eye health and development, suggests a recent study published in the journal JAMA Ophthalmology. It leads to choroidal thinning which can lead to macular holes and AMD. The study is a wake-up call adding to the reasons to ban smoking in any environment where children would be exposed.

The study demonstrated an association between secondhand smoke and thinning of choroidal thickness by 6 μm to 8 μm in children exposed to secondhand smoking. The thinning was dependent on the number of smokers in the family and the quantity of smoking. This suggests a dose-dependent relationship between the two (secondhand smoking and choroidal thickness).

The choroid is part of the eye between sclera and retina. It is a part of the uvea, and it contains blood vessels and connective tissue.

Secondhand smoking is a risk to adult ocular health, but its effect on children's ocular development is not known. Nan Yuan, The Chinese University of Hong Kong, Hong Kong, and colleagues assessed the association between choroidal thickness and secondhand smoking exposure in children.

For the purpose, the researchers recruited 1400 children aged 6 to 8 years from the population-based Hong Kong Children Eye Study at the Chinese University of Hong Kong Eye Centre from January 2016 to July 2017. 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.

Key findings of the study include:

• Of 1400 children, 941 (67.2%) had no exposure to secondhand smoking, and 459 (32.8%) had exposure to secondhand smoking.


• 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 an 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.

"These results support evidence regarding the potential hazards of secondhand smoking to children," concluded the authors.

More Information: "Association of Secondhand Smoking Exposure With Choroidal Thinning in Children Aged 6 to 8 Years - The Hong Kong Children Eye Study" published in the journal JAMA Ophthalmology.