Gender predisposition to myopia shifts to girls in the young generation.

Abstract

Purpose : Previous studies have suggested that female gender is a risk factor for myopia. The underlying mechanism is not well understood, and gender-specific factors such as age of growth spurt have been proposed. The aim of this study was to explore gender differences in myopia development in two prospective population-based cohorts from different generations, and to find possible explanations.

Methods : Analyses were performed in the birth cohort study Generation R (n=7229) and in the elderly Rotterdam Study I-III (45+ yrs; n=8674). Cycloplegic refraction was measured in the children at 6, 9, and 13 years, automated refraction was measured in the adults, and axial length and height was measured in both. Myopia was defined as spherical equivalent ≤-0.5D in at least one eye. Lifestyle factors including near work and outdoor exposure were assessed in the children and level of education in the adults, both by questionnaire. The association between gender and myopia was tested using Cox proportional hazards and logistic regression models adjusted for age; change in height, lifestyle factors and education were investigated as possible mediators.

Results : Myopia prevalence increased from 2.5%, to 11.5% and 22.5% at age 6, 9, and 13 years in the children, respectively; the prevalence was 30.6% in the adults. Female gender was associated with myopia in the children (HR=1.14 95% CI=1.02-1.27), but was inversely associated in the adults (OR=0.88 95%CI=0.80-0.96). Mediators of the association in children were outdoor exposure, growth in height, sport participation, reading time, and number of books read per month; these mediators together attenuated the effect of gender with 34.9% and reduced risk to HR=1.09 (95%CI=0.97-1.23). Education was the most important mediator of the association in adults, attenuating the effect with 89.7% to OR=0.98 (95%CI=0.90-1.09).

Conclusions : In our study, myopia was more common in girls in the young generation, but more common in men in the older generation. This paradigm shift and our mediation analysis provide compelling evidence that lifestyle factors and education are strong drivers of myopia. In the generations to come, particularly girls should be guided to adhere to protective behaviour.

This is a 2021 ARVO Annual Meeting abstract.