Age-related Macular Degeneration: Linked to Vitamin D Deficiency and Genetics

In women, age-related macular degeneration (AMD), an eye disease related to aging, affects more those with vitamin D deficiency, and this risk further increases in those genetically predisposed due to specific gene variants.

This was revealed in a study published in JAMA Ophthalmology by a team of researchers from the University at Buffalo (USA).

What is Age-related Macular Degeneration?

Age-related macular degeneration (AMD) is an eye disease related to deterioration of the macula, the central area of the retina. This damage can cause a drastic reduction in the visual field. The disease is the leading cause of progressive vision loss and blindness in the elderly in industrialized countries; in Italy, approximately 63,000 new AMD cases occur annually. The causes of this disease are diverse and represent a combination of genetic and environmental factors that contribute to macular aging. One of the main factors involved in AMD onset seems to be oxidative damage caused by free radicals, highly damaging and aggressive molecules for the body. In this regard, certain substances like antioxidant vitamins A, C, and E, and carotenoids can protect the retina from oxidative damage related to aging. Likewise, omega-3, polyunsaturated fatty acids essential for maintaining the structural and functional roles of the retina, appear to counteract the disease.

Vitamin D and Two Genes Also Influence Disease Onset

In recent years, three major studies, named AREDS, AREDS2, and CAREDS, demonstrated that increased intake of antioxidant nutrients such as vitamins C and E, zinc, copper, beta-carotene, and lutein and zeaxanthin—two carotenoids that are fundamental components of the macula—can significantly reduce AMD progression. Recently, it has been hypothesized that vitamin D deficiency may also increase the risk of this eye disease. The aim of this new study was to confirm and examine the association with vitamin D and the potential influence of genetic factors in this relationship. The study involved 913 women who participated in the CAREDS study. Between 10% and 30% of participants showed vitamin D deficiency (levels below 30 nmol/L) or insufficient levels (between 20 and 50 nmol/L).

Specifically, researchers examined in each subject the relationship between serum vitamin D levels, two different forms of the CFH gene believed to predispose to AMD, and the risk of developing age-related macular degeneration. The CFH gene is responsible for producing the homonymous protein involved in the immune response activated during the disease. Statistical analyses showed that women with deficient or insufficient vitamin D levels had a 2.6 and 1.5 times higher risk of developing AMD, respectively, and among them, the risk was highest in those with a high-risk form of the CFH gene.Women with vitamin D deficiency and both risk alleles of the CFH gene had a 6.7 times greater likelihood of developing AMD compared to those without genetic predisposition.

The Study Supports a Role for Vitamin D in Eye Health

According to the researchers, these results not only confirm that low blood levels of antioxidant nutrients predispose to AMD onset, but also suggest that genetic forms of vitamin D metabolism may influence the risk of developing the disease.

Source: Millen AE, Meyers KJ, Liu Z, Engelman CD, Wallace RB, LeBlanc ES, Tinker LF, Iyengar SK, Robinson JG, Sarto GE, Mares JA. Association between vitamin D status and age-related macular degeneration by genetic risk. 2015 JAMA Ophthalmol doi: 10.1001/jamaopthalmol.2015.2715