Analysis of Secondhand Smoke Exposure and Myopia Among Children Aged 6 to 8 Years in Hong Kong

Abstract

ImportanceSecondhand smoke (SHS) exposure potentially threatens ocular health; however, its association with myopia is unknown.ObjectiveTo examine the association between SHS exposure and childhood myopia.Design, Setting, and ParticipantsCross-sectional data from the population-based Hong Kong Children Eye Study were used. Data were collected from March 5, 2015, to September 12, 2021, at The Chinese University of Hong Kong Eye Center. Participants included children aged 6 to 8 years. Secondhand smoke exposure was evaluated using a validated questionnaire. All participants underwent comprehensive ophthalmic and physical examinations.ExposureSecondhand smoke exposure.Main Outcomes and MeasuresGeneralized estimating equations were constructed to examine the association of SHS exposure with spherical equivalent and axial length; logistic regression models, with myopia rate; and linear regression models, with myopia onset.ResultsA total of 12 630 children (mean [SD] age, 7.37 [0.88] years; 53.2% boys) were included in the analysis. Among the participants, 4092 (32.4%) had SHS exposure. After adjusting for age, sex, parental myopia, body mass index, near-work time, outdoor time, and family income, SHS exposure was associated with greater myopic refraction (β = −0.09 [95% CI, −0.14 to −0.03]) and longer axial length (β = 0.05 [95% CI, 0.02-0.08]). Children with SHS exposure were more likely to develop moderate (odds ratio [OR], 1.30 [95% CI, 1.06-1.59]) and high myopia (OR, 2.64 [95% CI, 1.48-4.69]). The association of SHS exposure with spherical equivalence and axial length was magnified in younger children. For each younger year of a child’s exposure to SHS, SHS exposure was associated with a 0.07-D decrease in spherical equivalence (β = 0.07 [95% CI, 0.01-0.13]) and a 0.05-mm increase in axial length (β = −0.05 [95% CI, −0.08 to −0.01]). Exposure to SHS was associated with an earlier mean (SD) age at onset of myopia (72.8 [0.9] vs 74.6 [0.6] months; P = .01). Every increase in SHS exposure in units of 10 cigarettes per day was associated with greater myopic refraction (β = −0.07 [95% CI, −0.11 to −0.02]), axial length (β = 0.04 [95% CI, 0.01-0.06]), and likelihood of developing moderate (OR, 1.23 [95% CI, 1.05-1.44]) and high myopia (OR, 1.75 [95% CI, 1.20-2.56]), and earlier myopia onset (β = −1.30 [95% CI, −2.32 to −0.27]).Conclusions and RelevanceThe findings of this cross-sectional study suggest that SHS exposure was associated with greater myopic refraction, longer axial length, greater likelihood of developing moderate and high myopia, and earlier myopia onset. The larger the quantity of SHS exposure and the younger the child, the more advanced myopia development and progression with which SHS exposure is associated.

The influence of the environment and lifestyle on myopia

“…The possible pharmacological causal pathway mediated via both nicotinic agonist and antagonist was also ill-defined [ 229 , 230 ]. Recently, a large cross-sectional study on 6–8-year-old Hong Kong children has shown an association of second-hand smoking exposure with both the onset and progression of myopia [ 231 ]. A small but dose-response effect of smoking was observed with an increase in 0.07 D myopia or 0.04 mm AL elongation with 10 cigarettes/day [ 231 ].…”

“…Recently, a large cross-sectional study on 6–8-year-old Hong Kong children has shown an association of second-hand smoking exposure with both the onset and progression of myopia [ 231 ]. A small but dose-response effect of smoking was observed with an increase in 0.07 D myopia or 0.04 mm AL elongation with 10 cigarettes/day [ 231 ]. The study was cross-sectional in design and could not prove a causal relationship.…”

Genetic causal association between type 2 diabetes, body mass index, smoking initiation and myopia：A mendelian randomization study

“…Chua SY et al found that exposure to passive smoking in Asian children from birth to 6 months of age slightly increases the risk of earlyonset myopia 31 . Another study in Hong Kong indicated that exposure to secondhand smoke was associated with higher myopic refraction, longer axial length, a greater probability of developing moderate and high myopia, and earlier onset of myopia 32 .However, S-M Saw's study did not nd a relationship between parental smoking and childhood refractive errors 33 .This MR study supports for the rst time a causal association between smoking initiation and myopia after adjusting for type 2 diabetes and BMI. This nding suggests that in addition to focusing on children's passive smoking, the initiation of children's smoking also deserves our attention in the eld of myopia development.It is worth noting that considering smoking's potential detrimental effects on the physical development of adolescents, we do not advocate smoking as a means of managing myopia.…”

The application of organoids in toxicity test of environmental pollutants

“…The main ways in which environmental pollutants enter the human body are through inhalation, ingestion and skin contact [3] . Some pollutants can also enter the human body through the mucous membranes of the eyes [4] , sweat glands and damaged wounds [5] . They can cause damage to multiple body systems and threaten human health (Fig.…”