Outdoor Activity Reduces the Prevalence of Myopia in Children
Received 4 September 2007; received in revised form 14 November 2007; accepted 14 December 2007. published online 21 February 2008.
Objective
To assess the relationship of near, midworking distance, and outdoor activities with prevalence of myopia in school-aged children.
Design
Cross-sectional study of 2 age samples from 51 Sydney schools, selected using a random cluster design.
Participants
One thousand seven hundred sixty-five 6-year-olds (year 1) and 2367 12-year-olds (year 7) participated in the Sydney Myopia Study from 2003 to 2005.
Methods
Children had a comprehensive eye examination, including cycloplegic refraction. Parents and children completed detailed questionnaires on activity.
Main Outcome Measures
Myopia prevalence and mean spherical equivalent (SE) in relation to patterns of near, midworking distance, and outdoor activities. Myopia was defined as SE refraction ≤−0.5 diopters (D).
Results
Higher levels of outdoor activity (sport and leisure activities) were associated with more hyperopic refractions and lower myopia prevalence in the 12-year-old students. Students who combined high levels of near work with low levels of outdoor activity had the least hyperopic mean refraction (+0.27 D; 95% confidence interval [CI], 0.02–0.52), whereas students who combined low levels of near work with high levels of outdoor activity had the most hyperopic mean refraction (+0.56 D; 95% CI, 0.38–0.75). Significant protective associations with increased outdoor activity were seen for the lowest (P = 0.04) and middle (P = 0.02) tertiles of near-work activity. The lowest odds ratios for myopia, after adjusting for confounders, were found in groups reporting the highest levels of outdoor activity. There were no associations between indoor sport and myopia. No consistent associations between refraction and measures of activity were seen in the 6-year-old sample.
Conclusions
Higher levels of total time spent outdoors, rather than sport per se, were associated with less myopia and a more hyperopic mean refraction, after adjusting for near work, parental myopia, and ethnicity.
Available online: February 21, 2008.
1School of Applied Vision Sciences, Faculty of Health Sciences, University of Sydney, Sydney, Australia.
2ARC Centre of Excellence in Vision Science and Research School of Biological Sciences, Australian National University, Canberra, Australia.
3Department of Ophthalmology (Centre for Vision Research, Westmead Hospital) and Westmead Millennium Institute, Sydney, Australia.
4Centre for Clinical Epidemiology and Biostatistics, University of Newcastle, Newcastle, Australia.
Correspondence and reprint requests to Dr Kathryn Rose, Discipline of Applied Vision Sciences, Faculty of Health Sciences, University of Sydney, PO Box 170, Lidcombe, NSW Australia, 1815.
Manuscript no. 2007-1147.
No conflicting relationship exists for any author.
The Sydney Myopia Study is supported by the National Health & Medical Research Council, Canberra, Australia (grant no. 253732), and Westmead Millennium Institute, University of Sydney, Sydney, Australia. Dr Morgan's contribution was supported by the Australian Research Council, Canberra, Australia (grant no. COE561903). The sponsors and funding organizations had no role in the design or conduct of the research.
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