Dataset Information

Birth order and myopia.

ABSTRACT: An association between birth order and reduced unaided vision (a surrogate for myopia) has been observed previously. We examined the association between birth order and myopia directly in four subject groups.Subject groups were participants in (1) the Avon Longitudinal Study of Parents and Children (ALSPAC; UK; age 15 years; N = 4401), (2) the Singapore Cohort Study of Risk Factors for Myopia (SCORM; Singapore; age 13 years; N = 1959), (3) the Raine Eye Health Study (REHS; Australia; age 20 years; N = 1344), and (4) Israeli Defense Force Pre-recruitment Candidates (IDFC; Israel; age 16-22 years; N = 888,277). The main outcome was odds ratios (OR) for myopia in first-born versus non-first-born individuals after adjusting for potential risk factors.The prevalence of myopia was numerically higher in first-born versus non-first-born individuals in all study groups, but the strength of evidence varied widely. Adjusted ORs (95% confidence intervals, CIs) were: ALSPAC, 1.31 (1.05-1.64); SCORM, 1.25 (0.89-1.77); REHS, 1.18 (0.90-1.55); and IDFC, 1.04 (1.03-1.06). In the large IDFC sample, the effect size was greater (a) for the first-born versus fourth- or higher-born comparison than for the first-born versus second/third-born comparison (p < 0.001) and (b) with increasing myopia severity (p < 0.001).Across all studies, the increased risk of myopia in first-born individuals was low (OR < 1.3). Indeed, only the studies with >4000 participants provided strong statistical support for the association. The available evidence suggested the relationship was independent of established risk factors such as time outdoors/reading, and thus may arise through a different causal mechanism.

SUBMITTER: Guggenheim JA

PROVIDER: S-EPMC3833053 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Birth order and myopia.

Guggenheim Jeremy A JA McMahon George G Northstone Kate K Mandel Yossi Y Kaiserman Igor I Stone Richard A RA Lin Xiaoyu X Saw Seang Mei SM Forward Hannah H Mackey David A DA Yazar Seyhan S Young Terri L TL Williams Cathy C

Ophthalmic epidemiology 20131029 6

<h4>Purpose</h4>An association between birth order and reduced unaided vision (a surrogate for myopia) has been observed previously. We examined the association between birth order and myopia directly in four subject groups.<h4>Methods</h4>Subject groups were participants in (1) the Avon Longitudinal Study of Parents and Children (ALSPAC; UK; age 15 years; N = 4401), (2) the Singapore Cohort Study of Risk Factors for Myopia (SCORM; Singapore; age 13 years; N = 1959), (3) the Raine Eye Health Stu ...[more]

PMID: 24168726

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Project description:Visual impairment due to myopia is an important public health issue. A prior analysis of population-based cohorts aged 15 to 22 years recruited from the United Kingdom and Israel suggested myopia and high myopia were approximately 10% more common in first-born compared with later-born children.To examine whether myopia was associated with birth order in an earlier generation than studied previously and, if so, whether the association was attenuated after adjusting for education exposure, as predicted by the hypothesis that the education of children with later birth orders is less intense.Cross-sectional study of UK Biobank participants recruited from 2006 to 2010. Analysis was restricted to participants aged 40 to 69 years who had a vision assessment, self-reported white ethnicity, and no history of eye disorders (N?=?89,120). Myopia and high myopia were defined as autorefraction of -0.75 diopters (D) or less and -6.00 D or less, respectively.Birth order and information on potential confounders including highest educational qualification ascertained using a structured questionnaire.Odds ratios (ORs) for myopia and high myopia by birth order, using logistic regression and adjusting for age and sex (model 1) or age, sex, and highest educational qualification (model 2).In model 1 (no adjustment for education), birth order was associated with both myopia and high myopia (eg, comparing first- vs second-born individuals; OR, 1.12; 95% CI, 1.08-1.16; P?=?1.40E-11 and OR, 1.21; 95% CI, 1.11-1.30; P?=?3.60E-06 for myopia and high myopia, respectively). The risk for myopia became progressively lower for later birth orders, suggesting a dose response. In model 2 (after adjusting for education), the effect sizes were attenuated by approximately 25% (OR, 1.09; 95% CI, 1.05-1.12; P?=?1.30E-06 and OR, 1.15; 95% CI, 1.06-1.25; P?=?4.60E-04 for myopia and high myopia, respectively) and the apparent dose response was abolished.These data suggest that the association between birth order and myopia is not due to a new environmental pressure in the last 30 to 40 years. The attenuated effect size after adjusting for educational exposure supports a role for reduced parental investment in education of children with later birth orders in their relative protection from myopia.

Dataset Information

Birth order and myopia.

Publications

Birth order and myopia.

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