Abstract
Purpose:
Reduced time spent outdoors is a risk factor for myopia, including in Avon Longitudinal Study of Parents and Children (ALSPAC) participants. One hypothesized mechanism involves variations in vitamin D levels being causally linked to myopia development or progression. Two case-control studies, one of White US (n=370) and one of Indian subjects (n=400), have reported that polymorphisms in the vitamin D receptor (VDR) gene are associated with risk of myopia: however the polymorphisms are not known to tag functional variants and, conversely, reportedly functional variants were not associated with myopia. We sought to investigate these associations in a larger sample of individuals.
Methods:
We included ALSPAC participants whose genetic data indicated White European ancestry and for whom refractive estimates using non-cycloplegic autorefractions had been obtained at visits to a research clinic (ages 7, 10, 11, 12 and 15 years). Subjects were classified as myopic (<=-1.00 D) or non-myopic (>-1.00 D) at each age they attended. We used survival analysis to investigate whether any of 11 SNPs in VDR predicted the development of myopia in the 9101 participants with at least one refractive estimate.
Results:
Five of the 11 VDR SNPs were associated with incident myopia (P=0.04 to 0.003). In all cases the effect size was small (Hazard Ratio<1.14). All associated SNPs were in linkage disequilibrium (r2=0.22-0.99) and conditional analyses suggested they had non-independent effects.
Conclusions:
All 5 VDR SNPs identified in this study may tag a single myopia-associated variant and were different from those identified in the previous studies. Three of the associated SNPs (rs731236, rs7975232, rs1544410) reportedly tag a functional variant that reduces VDR mRNA stability, consistent with their association with an increased risk of incident myopia. The variability between ours and other studies’ results suggests the need for further replication. Analysis of vitamin D levels for the participants should help clarify whether this represents a potentially modifiable causal pathway leading to myopia.
Keywords: 605 myopia •
539 genetics •
677 refractive error development