Genetics factor in vitamin D, AMD link

Seattle-Adequate levels of vitamin D can decrease the risk of age-related macular degeneration (AMD), but most markedly in individuals with two risk alleles for the CFH Y402H genotype, said Amy Millen, PhD.

Specifically, the association between serum [25(OH)D] and AMD is modified by the presence of the CFH Y402H polymorphism.

“Previous studies have shown a relationship between vitamin D and AMD,” said Dr. Millen, assistant professor, Department of Social and Preventive Medicine at the University at Buffalo, New York. “We looked to see if it was modified by the genetic risk of AMD.”

Among postmenopausal women with two risk alleles, those who had the highest concentrations of 25 (OH)D (at least 75 nmol/L) lowered the odds for AMD by 64%, Dr. Millen said.

AMD is a complex disease with both demographic and environmental risk factors that include age, diet, and smoking, as well as genetic risk factors. The CFH Y402H polymorphism has been associated with increased risk of AMD.

Data from the Carotenoids in Age-Related Eye Disease Study, an ancillary study of the Women’s Health Initiative, was used to evaluate the relationship between AMD risk of high versus low vitamin D status, and genetic components.

Previously, results from this study had suggested that higher levels of circulating vitamin D appeared to reduce the risk for early onset of AMD in this population.

This analysis included 1,230 postmenopausal women aged 50 to 79 years at study baseline, who had complete genotype data and available serum samples. The presence of AMD (n = 249) was evaluated 6 years later

Among women with inadequate ([25(OH)D]<30 nmol/L) or adequate ([25(OH)D]>75 nmol/L) vitamin D status, the presence of  two risk alleles was associated with an increased odds of AMD. However, these odds were attenuated in those with adequate vitamin D status (OR = 4.30 and OR = 1.56, respectively).

For noncarriers and women with one risk allele, the odds of AMD was lower in those with [25(OH)D]>75 (OR = 0.82 and OR = 0.89,respectively).

But in those with two risk alleles, the greatest effect for vitamin D was observed, Dr. Millen said. Having [25(OH)D]>75 lowered the odds for (OR = 1.56), as compared with those with 25(OH)D]<30.

“These data will need to be replicated,” Dr. Millen said.

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