Risk for macular degeneration linked to low levels of vitamin D

High concentrations of 25-hydroxyvitamin D may be linked to a lower risk for age-related macular degeneration (AMD), according to a systematic review and statistical analysis of several studies published April 2 in the European menopause online journal Maturitas.

The review and analysis, "Circulating vitamin D concentration and age-related macular degeneration: Systematic review and meta-analysis," by its authors at Angers University Hospital in France, looked at 11 previous studies since 2007 on the link between vitamin D and AMD. The studies ranged in participant size from 65 to 17,405 people. The numbers of participants in the studies with AMD (whole, early or late) ranged from between 31 to 1,440 people.

Among the review and analysis highlights in the abstract:

• Vitamin D may be involved in ocular health and function.
• High concentrations of 25-hydroxyvitamin D are associated with less AMD.
• Concentrations of 25-hydroxyvitamin D under 50nmol/L are associated with late-stage AMD.
• These findings provide a scientific basis for vitamin D replacement trials.

"In conclusion, this meta-analysis provides evidence that high 25OHD concentrations may be protective against AMD, and that 25OHD concentrations below 50nmol/L are associated with late AMD," the authors say.

Exploring the link

Past studies have seemed to link lower levels of vitamin D with AMD, especially for women, says Steven Ferrucci, O.D., chief of optometry at Sepulveda VA Medical Center and professor at Southern California College of Optometry at Marshall B. Ketchum University.

"This review revealed patients with AMD had, on average, lower levels of vitamin D in the blood stream than those patients who did not have AMD," says Dr. Ferrucci, who has written and lectured extensively on AMD. "Patients with low vitamin D levels had two times the risk of late AMD versus those with higher concentrations."

He adds, "Although it appears that low vitamin D levels may contribute to AMD, the authors are careful to point out it is not clear at this time if vitamin D supplementation would be protective against developing AMD. Further, they point out that the link between vitamin D deficiency and AMD is lacking—it may be that lower vitamin D is a result of AMD, and not a risk factor for its development."

Dr. Ferrucci says more research is needed into the cause and effect.

"Studies, such as this, highlight the growing interest in understanding the factors responsible for AMD onset and progression," he says. "As the population ages, finding safe and inexpensive ways to slow down or halt the progression of AMD is paramount. However, while this study is interesting, more research would need to be done before recommending vitamin D supplementation for AMD patients or at-risk patients on a large scale."

The AOA follows all research closely, including potential AMD treatments. Although vitamin D is an interesting treatment possibility for patients, more research is needed regarding its influence on visual health.