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Katie M Williams, Pirro G Hysi, Robert Plomin, Christopher J Hammond; Prevalence of myopia in an adolescent British cohort and cognitive associations during childhood. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3628.
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© ARVO (1962-2015); The Authors (2016-present)
To report the prevalence of refractive error in an adolescent British cohort, and to examine the influence of cognition over childhood development on myopia risk
The Twins Early Development Study is a longitudinal cohort of 10,000 British twins enrolled at birth between 1994-96, who have been studied from a neurodevelopmental perspective using multivariate quantitative and molecular genetic techniques. A sample of 2,625 pairs (aged 16-18) was invited to participate (52% response rate) and consent requested to contact their optometrist for subjective refraction data (87% response rate). Myopia was defined as spherical equivalent (SE) ≤-0.75 D, high myopia if ≤-6.0 D and hyperopia as ≥1.0 D. Multivariable regressions and mixed effect models were used to assess demographic features and associations during childhood (adjusted for age, sex, ethnicity, maternal education & family structure).
SE data was obtained on 1992 subjects. Responders reflected the UK population (95% European, 55% female). Mean SE was -0.35 D (SD 1.80). In those aged 16-18, 32.2% (95% CI 30.0-34.9) were myopic, 1.6% (95% CI 1.0-2.4) were highly myopic and 8.4% (95% CI 7.0-9.9) were hyperopic. Significant odds ratios (OR) for myopia were identified for age (1.72), non-white ethnicity (3.06) and maternal education (1.13). In a mixed effect model of composite scores of cognitive ability (g) at 2,3,4,7,10,12,14 & 16, the association with myopia was greatest in late adolescence (age 16: β -0.287 p=0.03). Association between upper quartile cognitive ability and myopia tended to become significant with age: age 4 (OR 1.15 p=0.51), age 7 (OR 1.45 p=0.11), age 10 (OR 1.68 p=0.05) and age 16 (OR 2.11 p=0.003). Verbal cognition (VC) was consistently more associated with myopia than non-verbal cognition (NVC), with greatest disparity and effect at younger ages (VC age 10 OR 1.26 [p=0.03] vs NVC OR 1.02 vs VC OR age 16 1.05). Bivariate twin modelling suggested shared genetic effects underlying SE and g.
Myopia prevalence in a UK-representative population of 16-18 year-olds is 32%. This suggests subsequent prevalence in adulthood may be higher than previous estimates, congruous with a cohort effect. A consistent and significant association of cognition for myopia was identified, with verbal cognition in early childhood and overall cognitive ability in adolescence most strongly associated with myopia risk.
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