Sunlight, lack of antioxidants tied to eye disease

NEW YORK (Reuters Health) - A combination of sunlight exposure and low blood levels of antioxidants may make older adults more vulnerable to a common vision-robbing disease called age-related macular degeneration, or AMD, researchers have found.

In a study of older adults from seven European countries, investigators found that among those with relatively low antioxidant levels, sun exposure was linked to an increased risk of advanced AMD. There was no such link seen in people with high antioxidant levels.

AMD is the leading cause of vision loss in older adults; it arises from gradual damage to the macula, a structure on the retina that allows for seeing fine detail.

The retina is the light-sensitive tissue at the back of the eye, and while much of the sun’s UV radiation is absorbed by outer eye structures, the retina is exposed to visible light -- in particular, blue light.

Studies have, however, generally failed to find a connection between sun exposure and AMD risk.

The new findings are the first to suggest that sun exposure may raise AMD risk in people with low antioxidant levels, according to lead researcher Dr. Astrid Fletcher, a professor at the London School of Hygiene & Tropical Medicine in the UK.

Fletcher and colleagues found that among the one-quarter of study participants with the lowest total antioxidant levels, the risk of AMD rose in tandem with their long-term exposure to blue light from the sun.

Lab research indicates that antioxidants like vitamins C and E, zinc and lutein are important in protecting the retina from the toxic effects of light, Fletcher told Reuters Health. So, she explained, it is biologically plausible that the combination of high sun exposure and low antioxidant levels contributes to AMD risk.

For their study, published in the Archives of Ophthalmology, the investigators assessed 4,753 adults ages 65 and up, roughly half of whom had AMD.

To estimate the participants’ long-term exposure to blue light, the researchers asked them about their typical sun exposure during their working life and retirement -- including whether they habitually wore a hat or sunglasses outdoors. The men and women also gave blood samples to be measured for antioxidant concentrations.

In general, the researchers found, participants with the lowest levels of vitamin C, vitamin E, zinc and zeaxanthin combined appeared vulnerable to blue light exposure. For every unit increase in blue light exposure, their risk of AMD climbed by 40 percent.

The findings should offer older and middle-aged adults more incentive to pack their diets with antioxidant-rich foods -- something that is already recommended for overall health, Fletcher noted.

“They should ensure that their diet regularly includes dark green, leafy vegetables -- such as spinach or greens -- orange or yellow bell peppers, citrus fruits, vegetable oils (and) nuts, for example,” Fletcher advised.

“There is no need to take supplements,” she added, “because adequate levels can be achieved by diet alone.”

Wearing a wide-brimmed hat and sunglasses will also help shield the eyes from the sun, the researchers note.

SOURCE: Archives of Ophthalmology, October 2008.