Myopia and the urban environment: Findings for a sample of 12-year old Australian school children

¹ Department of Ophthalmology and the Westmead Millennium Institute, Centre for Vision Research, University of Sydney, Sydney, New South Wales, Australia
² School of Applied Vision Sciences, Faculty of Health Sciences, University of Sydney, Sydney, New South Wales, Australia; University of Sydney, PO Box 170, Sydney, 1825, Australia
³ ARC Centre of Excellence in Vision Science and Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory, Australia
⁴ Dept of Ophthalmology and the Westmead Millennium Institute, Centre for Vision Research, University of Sydney, Sydney, New South Wales, Australia

^* To whom correspondence should be addressed. E-mail: paul_mitchell{at}wmi.usyd.edu.au.

	Abstract

Purpose: To examine associations between myopia and measures of urbanization in a population-based sample of 12-year-old Australian children Methods: Questionnaire data on socio-demographic and environmental factors including ethnicity, parental education, and time spent in near-work and outdoor activity were collected from 2367 children (75.0% response) and their parents. Population density data for the Sydney area were used to construct 5 urban regions. Myopia was defined as spherical equivalent refraction -0.50 diopters. Results: Myopia prevalence was lowest in the outer suburban region (6.9%) and highest in the inner city region (17.8%), with mean refraction tending toward greater myopia by region (outer suburban to inner city), after adjusting for age, gender, ethnicity, near-work, outdoor activity and parental myopia. Multivariate-adjusted analyses confirmed greater odds for myopia in regions of higher population density (ptrend=0.0001). Myopia was significantly more prevalent among children living in apartment residences than other housing types (2<0.0001), after adjusting for ethnicity, near-work and outdoor activity. Housing density (measured as number of houses visible from front door) was not significantly associated with myopia (2=0.1). For both European Caucasian and East Asian children, myopia was most prevalent in the inner city region (8.1% and 55.1%, for European Caucasian and East Asian, respectively). Conclusions: The higher myopia prevalence in inner city/urban areas compared to outer suburban areas for this large childhood sample suggest that even moderate environmental differences within a predominant suburban setting may be associated with increased odds of myopia. These findings are consistent with previous reports of rural-urban differences in childhood myopia.

Key Words: myopia, epidemiology, refractive error, children-s vision, visual development, statistics