Postnatal passive smoking and risk of myopia in children and adolescents: A systematic review and meta-analysis of observational studies.

OBJECTIVES

The relationship between postnatal passive smoking (secondhand smoke, SHS) and myopia in children remains uncertain, with inconsistent findings across studies and concerns regarding exposure measurement and confounding. This meta-analysis was performed to systematically evaluate the above association and role of potential confounding factors.

METHODS

PubMed, Embase, Web of Science, Wanfang, and CNKI were searched for relevant studies. Random-effects models were applied to pool odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Eleven studies were included. Overall, passive smoking was not significantly associated with myopia (OR = 1.00, 95% CI 0.82-1.20; I² = 81%). However, cohort studies showed a significant association (OR = 2.13, 95% CI 1.09-4.17; I² = 7%), whereas cross-sectional studies did not (OR = 0.95, 95% CI 0.78-1.14; I² = 83%; p for subgroup difference = 0.02). Regional differences were observed, with a nonsignificant trend toward increased risk in Asian populations and an inverse association in non-Asian studies. No significant effect modification was detected by age, refraction method, adjustment status, or study quality. Notably, exposure assessment relied predominantly on parental self-report, and adjustment for key confounders (e.g., outdoor time, near-work, parental myopia) was inconsistent across studies.

CONCLUSIONS

Overall, the available evidence does not support a consistent association between passive smoking and myopia. However, findings from cohort studies-which are more appropriate for risk inference due to their longitudinal design-suggest a potential association that cannot be excluded. Given the limited number of such studies, these results should be interpreted cautiously and considered hypothesis-generating.