38 W.C.J. Low, T.Y. Wong and S.-M. Saw

lower prevalence of myopia (12.4% vs. 25.4%; p = 0.004) and more hyperopic mean SE refractions (1.83 ± 0.24 vs. 0.96 ± 0.27 D; p = 0.02) than those whose parents never smoked. If one or more parents smoked during pregnancy, their children had a lower prevalence of myopia (8.6% vs. 23.9%; p = 0.003) and more hyperopic mean SE refractions (2.19 ± 0.34 vs. 1.07 ± 0.22 D; p = 0.006) than those whose parents never smoked. Multivariate OR for myopia was 0.22 (95% CI = 0.07–0.64; p = 0.008) when either parent currently smoked, 0.15 (95% CI = 0.04–0.53; p = 0.003) when one of the parents smoked during pregnancy, and 0.22 (95% CI = 0.08–0.59; p = 0.003) when either parent smoked during their child’s lifetime, after adjusting for the child’s age, BMI, weighted near work, parental myopia, and parental education.

In a population-based cross-sectional study of 6491 Chinese adults aged 30 to 99 years from Handan, China, Liang and co-workers (Table 6)50 found that the multivariate OR for myopia was 0.7 (95% CI = 0.5–0.9; p = 0.003) in adults who currently smoked compared with those who never smoked after controlling for age, history of diabetes, smoking, hours of reading per day, and number of family members with myopia.

Breastfeeding

In a population-based cross-sectional study of 2639 Chinese preschool children aged 6 to 72 months from the Strabismus, Amblyopia and Refractive Error Study (STARS) in Singapore, Sham and co-workers (Table 7)51 demonstrated that a history of breastfeeding lowered the SE refraction by 0.12 D (standard error = 0.06; p = 0.03) after adjusting for age, gender, history of breastfeeding, outdoor activity, mother’s education, mother’s smoking history, parental myopia, birth weight, maternal age, and child’s height. However, breastfeeding was not associated with myopia (defined as SE at least –0.5 D) after controlling for the same confounders (OR = 0.85; 95% CI = 0.62–1.18).

The SCORM investigated 797 school children aged 10 to 12 years and reported that the multivariate OR of myopia (defined as SE at least –0.5 D) for breastfed children was 0.58 (95% CI = 0.39–0.84) after adjusting for the child’s age, sex, race, birth weight, height, number of books read per week, IQ scores, mother’s education, parental myopia, maternal age at delivery, household income, and clustering of siblings within family (Table 7).52 Moreover, the mean SE refraction of breastfed