MONDAY, May 10, 2004 (HealthDayNews) -- People who develop age-related macular degeneration tend to die earlier than those who don't get the vision-robbing disease, a new study reports.
Why this happens isn't known, but experts suspect eye problems such as age-related macular degeneration (AMD) and cataracts may be a sign of early aging or other pervasive systemic health problems, such as heart disease.
"This study confirms what other studies have shown, that people who have cataracts are more likely to die than people who don't," said lead researcher Dr. Frederick L. Ferris III, clinical director of the National Eye Institute. "A new finding is that the same is true for AMD."
AMD is the loss of central vision due to changes, often related to aging, in the macula, which is the back portion of the retina responsible for clear, sharp vision. This central vision is used for "straight-ahead" activities such as reading, sewing and driving.
Ferris and his colleagues collected data on people who participated in the Age-Related Eye Disease Study. This research included 4,753 people, aged 55 to 81. Some of the subjects were randomly assigned to receive high-dose antioxidants, zinc, antioxidants plus zinc or a placebo.
During a period of 6.5 years, 534 patients died, according to the report in the May issue of Archives of Ophthalmology.
The research team found people with AMD had about a 41 percent increased risk of death compared with those without AMD. In addition, the deaths of those with advanced AMD were mostly from heart disease.
Patients with poor vision had about a 36 percent increased risk of death; and those who had cataract surgery had a 55 percent increased risk, Ferris's group found.
Those patients who received zinc had a 27 percent lower mortality rate, compared with those who did not receive the mineral.
Ferris said the findings might indicate that people with AMD are aging faster than those without AMD; they may also indicate other ongoing disease.
"There is nothing here that says that if you have AMD or a cataract you are about to die," Ferris cautioned. "But this finding may be useful in understanding the aging process."
As for the association of zinc with longer life, Ferris couldn't explain the possible connection. "It may be a chance finding," he said.
Dr. Stephen R. Russell is an associate professor of ophthalmology at the University of Iowa. "We have known for a long time that patients with AMD have higher incidence of cardiovascular disease, and they are also weaker than normal," he said.
Why this is the case isn't known, he added, "but it does go along with the idea that there is general systemic disease."
Another study in the journal confirms research that sunlight has no effect on the development of macular degeneration.
In this study, researchers collected data on the association between sunlight exposure and sunlight sensitivity and the incidence of AMD in people aged 43 to 86 who participated in the so-called Beaver Dam Eye Study. Of all the subjects, 3,684 were followed for five years, and 2,764 were followed for 10 years.
"We failed to find any relationship between light exposure and AMD," said lead researcher Dr. Ronald Klein, a professor of ophthalmology and visual sciences at the University of Wisconsin Medical School.
"Although there is not a strong association between light exposure and AMD, there seems to be some evidence that earlier sunlight exposure may increase the risk of developing signs of AMD," he said, but he added he's not sure why that's the case.
Klein's team found that people who reported more than five hours of sun exposure a day during their teens, 30s and at the beginning of the study were more than three times likely to develop early stages of AMD within 10 years.
And those who reported more than 10 severe sunburns during their youth were 2.5 times more likely than those who experienced one or no sunburns to develop AMD within 10 years, the researchers found.
Klein said the study found no relationship between UV-B ray exposure, winter leisure time spent outdoors, skin sun sensitivity and the risk for AMD.
Since the findings weren't consistent, Klein said, he wasn't able to draw any definitive conclusions about exposure to sunlight and the risk of developing AMD.
Russell added, "This has been a controversy for several decades."
However, he agreed with Klein that light exposure is not related to the development of AMD. "Sunlight gets a bad rap," he said.
"Rather, AMD is probably a systemic disease, which is not directly related to light exposure," Klein said.
The Foundation Fighting Blindness has information about vision problems.