Published in Research

Is secondhand smoking tied to pediatric myopia?

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3 min read

A new study published in JAMA Ophthalmology led by researchers from The Chinese University of Hong Kong assessed the association between secondhand smoke (SHS) exposure and pediatric myopia.

Talk about the study.

In this cross-sectional study, researchers analyzed data from the population-based Hong Kong Children Eye Study and included 12,630 children between the ages of 6 and 8.

Exposure to SHS was measured using questionnaires, which also recorded information about the child’s age at myopia onset, daily living routine, living environment, lifestyle, daily time spent outdoors, and near work.

And the participants?

Within the SHS exposure group, on average, children had a greater body mass index (BMI), birth weight, and near-work time.

Additionally this group had a lower prevalence of parental myopia, lower family income, and parental educational levels. On average, household members smoked a mean of 10.5 cigarettes daily.

Findings?

Among the participants, 4,092 (32.4%) were exposed to SHS, and—after adjusting for confounding variables,—SHS exposure was associated with greater myopic refraction (β= -0.09 [95% confidence interval (CI), -0.14 to -0.03]) and longer axial length (β= 0.05 [95% CI, -0.02 to -0.08]).

Additionally, children exposed to SHS 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]).

Tell me more.

Further, the link between SHS exposure with spherical equivalence and axial length was magnified in younger pediatric patients.

For every year earlier of a child’s exposure to SHS, there was an associated 0.07 diopter 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]).

Anything else?

SHS exposure was associated with an earlier mean age of onset of myopia (72.8 [0.9] vs. 74.6 [0.6] months, P= 0.01).

Every increase in SHS exposure, in units of 10 cigarettes per day, was linked with the following:

  • Greater myopic refraction (β= -0.07 [95% CI, -0.11 to -0.02])
  • Increased axial length (β= 0.04 [95% CI, 0.01-0.06])
  • Likelihood of developing moderate myopia (OR, 1.23 [95% CI, 1.05-1.44])
  • Likelihood of developing high myopia (OR, 1.75 [95% CI, 1.20-2.56])
  • Earlier age of myopia onset (β= -1.30 [95% CI, -2.32 to -0.27])

Limitations?

Researchers considered SHS exposure status a binary variable without specifying which of the family members smoked.

Interestingly, paternal smoking contributed dominantly to SHS exposure (>80%).

Due to the limited rate (~5%) and power of maternal smoking, the association of parental gender, smoking status, and pediatric myopia was not measured.

Significance?

Based on these findings, educating parents on the inherent risks associated with SHS is highly recommended, particularly those with young children to reduce the potential for myopia development.