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Study shows first-born children more likely to be myopic
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An analysis of nearly 90,000 adults in the U.K. indicates that first-born individuals were 10% more likely to have myopia and 20% more likely to have high myopia than their younger siblings.
Guggenheim and colleagues stated in JAMA Ophthalmology that an earlier study came to similar conclusions, but they wanted to determine if this association was a result of “new environmental pressure in the last 30 to 40 years.”
The researchers performed a cross-sectional study of U.K. Biobank participants that were recruited from 2006 to 2010. The 89,120 subjects were between 40 and 69 years old, had a vision assessment, were white and had no history of ocular disorders. They defined myopia as an autorefraction of -0.75 D or less and high myopia as -6.00 D or less, according to the study.
Guggenheim and colleagues found when no adjustment was made for the subjects’ education level, birth order was associated with all myopia. After adjusting for education, the effect sizes were reduced by about 25% and the apparent dose response was abolished.
“The results replicate earlier findings from two contemporary international cohorts of adolescents and young adults, implying that the cause of the birth order-myopia association is widespread and has been in existence for several decades,” the authors said in the study. “The association was larger before adjusting for educational exposure, suggesting that reduced parental investment in the education of children of later birth order may be partly responsible.” – by Nancy Hemphill, ELS, FAAO
Disclosures: The authors report no relevant financial disclosures.
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