In the news: Vitamin D Linked to AMD by Genetic Risk: Vitamin D Status & Glaucoma

Low Vitamin D Status & Ocular Conditions

The findings of two newly published studies suggest that inadequate blood levels of vitamin D may be a risk factor in ocular diseases.

Vitamin D Insufficiency & AMD Genetic Risk

Vitamin D, with its anti-inflammatory and immune modulating activities, is theorized to play a protective role in the development of age-related macular degeneration (AMD). Several studies have noted a relationship between low blood levels of the vitamin and greater likelihood of AMD. In the Carotenoids in Age-Related Eye Disease Study (CAREDS), for example, the odds for AMD were increased in postmenopausal women who had low vs. high vitamin D status assessed by intake and blood levels.

These findings led University of Buffalo investigators to examine whether that observed association was stronger in women with established AMD risk genotypes. They also determined whether AMD is associated with single nucleotide polymorphisms (SNPs) involved in the transport, metabolism and genomic functions of vitamin D (1).

Nine hundred and thirteen CAREDS participants were included in the analysis. Of these, 550 had adequate vitamin D levels (> 20 ng/mL), 275 had inadequate or suboptimal levels (> 12 to < 20 ng/mL), and 88 were deficient (< 12 ng/mL).

When looking at vitamin D status and AMD risk alone, deficiency was associated with a 2.6-fold increased odds of AMD compared with adequate status. Suboptimal levels increased the odds of AMD 1.5 fold vs. adequate levels.

When assessing the joint effects of vitamin D status and genetic risk, a 6.7-fold increased odds of AMD was seen in vitamin D deficient women who had 2 risk alleles for CFH (Y202H). For deficient women with 2 high-risk CFI alleles (rs10033900), the odds were 6.3- fold higher. None of the vitamin D genes assessed affected the odds of AMD.

This is the first study to explore the interaction between genetic risk of AMD and vitamin D status. While the study had limitations – notably the small number of cases in the joint effects analyses, the results suggest synergy between vitamin D and high-risk genotypes of the complement cascade. It’s possible that maintaining sufficient vitamin D levels could help prevent AMD, especially in people at high genetic risk.

Vitamin D Status & Presence of Glaucoma

In non-human primates, vitamin D drops have been reported to lower intraocular pressure by 20%, raising the possibility of a link between vitamin D and primary open-angle glaucoma (POAG). Spurred by this report and others related to vitamin D and AMD, university medical researchers from Singapore and France teamed to determine whether vitamin D insufficiency is associated with the presence and severity of POAG (2). This case control study of older adults included 150 cases of moderate-to-severe POAG and 164 age-matched healthy controls.

Compared to controls, the POAG group had lower vitamin D blood levels – about 15% lower than controls, and a greater prevalence of vitamin D inadequacy. Higher mean vitamin D concentrations were associated with lower POAG frequency, even after adjustment for potential confounders. Similarly, low vitamin D status was associated with a 2-fold increase in POAG. No significant difference in vitamin D blood levels between moderate and severe POAG was seen.

This study found low vitamin D levels to be directly associated with the presence, though not severity, of POAG. The authors call for prospective observational studies and clinical interventions to determine whether vitamin D plays a role in POAG development.

References

1. Millen AE, et al. Association between Vitamin D status and age-related macular degeneration by genetic risk. JAMA Opththalmol. Epub Aug. 27, 2015.
2. Goncalves A, et al. Serum vitamin D status is associated with the presence but not the severity of primary open angle glaucoma. Maturitas 81:470-74, 2015.