Abstract
Purpose: :
To examine the associations of maternal smoking with refraction in children aged 6 and 12 years.
Methods: :
Children from 34 primary and 21 high schools in Sydney, Australia, were examined in the Sydney Myopia Study. 1402 of 1741 6-year old participants and 1872 of 2367 12-year old participants of predominantly European Caucasian and Middle Eastern ethnicities were included in this analysis to examine a relatively homogenous distribution of Axial length (AL).Comprehensive eye exams included cycloplegic autorefraction and ocular biometry. Information on maternal smoking history (years smoked and number of cigarettes smoked/ day during pregnancy) and birth parameters were obtained from questionnaires completed by parents.
Results: :
315 12-year old and 186 6-year old children were exposed to maternal smoking prior to birth. After adjusting for age, sex and ethnicity, history of maternal smoking was significantly associated with low birth weight (12-year olds: mean birth weight 3229g in the exposed vs 3401g in the non-exposed, p<0.0001; 6-year-olds: mean 3171g in exposed vs. 3388g in non-exposed children, p<0.0001). Similarly, history of maternal smoking was associated with slightly shorter AL (12-year olds: age-sex-ethnicity adjusted mean 23.28mm vs 23.38mm in non-exposed, p=0.005; 6-year olds: adjusted mean 22.49mm vs 22.62mm in non-exposed, p=0.008). This association remained significant only in the 12-year olds (p=0.03) but not in the 6-year olds (p=0.24) after further adjusting for birth weight. After adjusting for ethnicity, age, sex and birth weight, exposure to maternal smoking was associated with a more hyperopic refraction (12-year olds: mean spherical equivalent refraction [SER] 0.77 D vs 0.58D in non-exposed, p=0.003; 6-year olds: mean SER 1.42D vs 1.19D in non-exposed, p=0.003), after further adjusting for AL, this association remained significant only in the 6-year olds (p=0.003).
Conclusions: :
Our findings suggest that exposure to maternal smoking during pregnancy is associated with low birth weight, shorter AL and more hyperopic refraction in children. The association of maternal exposure to smoking with low birth weight could not explain entirely its association with shorter AL in the 12-year olds; and its association with shorter AL could not explain entirely its association with hyperopic refraction in the 6-year olds.
Keywords: refraction • clinical (human) or epidemiologic studies: risk factor assessment