Does vitamin D mediate the protective effects of time outdoors on myopia? Findings from a prospective birth cohort

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Abstract

Purpose: More time outdoors is associated with a lesser risk of myopia but the underlying mechanism is unclear. We tested the hypothesis that 25-hydroxyvitamin D (vitamin D) mediates the protective effects of time outdoors against myopia. Methods: We analyzed data for children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) population-based birth cohort: Non-cycloplegic autorefraction at age 7 to 15 years; maternal report of time outdoors at age 8 years and serum vitamin D2 and D3 at age 10 years. A survival analysis hazard ratio (HR) for incident myopia was calculated for children spending a high vs. low time outdoors, before and after controlling for vitamin D level (N=3,677). Results: Total vitamin D and D3, but not D2, levels were higher in children who spent more time outdoors [mean (95% CI) vitamin D in nmol/l: Total, 60.0 (59.4 to 60.6) vs. 56.9 (55.0 to 58.8), P=0.001; D3, 55.4 (54.9 to 56.0) vs. 53.0 (51.3 to 54.9), P=0.014; D2, 5.7 (5.5 to 5.8) vs. 5.4 (5.1 to 5.8), P=0.23]. In models including both time outdoors and sunlight-exposure-related vitamin D, there was no independent association between vitamin D and incident myopia [Total, HR=0.83 (0.66 to 1.04), P=0.11; D3, HR=0.89 (0.72 to 1.10), P=0.30], whilst time outdoors retained the same strong negative association with incident myopia as in unadjusted models [HR=0.69 (0.55 to 0.86), P=0.001]. Conclusions: Total vitamin D and vitamin D3 were biomarkers for time spent outdoors, however there was no evidence they were independently associated with future myopia.

Original languageEnglish
JournalInvestigative Ophthalmology and Visual Science
DOIs
Publication statusPublished - 18 Nov 2014

Bibliographical note

Copyright © 2014 by Association for Research in Vision and Ophthalmology.

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