May 10, 2004 -- Spending too much time outdoors in the summer sun may raise the risk of a common sight-robbing disease later in life, according to a new study.
Researchers found that people who spent a lot of time in the summer sun in their teens, 30s, and after age 40 were twice as likely to develop an early form of age-related macular degeneration than those who stayed out of the sun.
However, the study also suggests that protective measures, such as wearing a hat and sunglasses, can dramatically reduce some of those additional sun-related risks.
Age-related macular degeneration is the leading cause of vision loss in older people, and few treatments are available for the disease. The condition leads to an abnormal growth of blood vessels and opaque deposits on the retina, the light-sensitive layer of cells located at the back of the eye. It also causes an increase in the amount of pigment in the retina.
The precise cause of the disease is unknown, but a combination of genetic and environmental factors is thought to play a role.
Summer Sunlight Linked to Macular Degeneration
In the study, researchers looked at the association between sunlight exposure and the 10-year risk of age-related macular degeneration among a large group of adults aged 43 to 86 years who were first examined between 1988 and 1990 as a part of the Beaver Dam Eye Study.
The results appear in the May issue of The Archives of Ophthalmology.
Researchers found that people who spent more than five hours a day in the summer sun in their teens, 30s, and after age 40 were more than twice as likely to develop early age-related macular degeneration compared with those who reported spending less than two hours per day of sunlight during the same periods.
In addition, those who got five or more hours per day of summer sun were more than three times as likely to develop increased retinal pigment, a condition commonly associated with age-related macular degeneration.
But the study showed wearing hats or sunglasses at least half of the time reduced the risk of developing deposits on the retina by 50% among those who reported the highest sun exposure levels.
The study also found that people who had more than 10 severe sunburns in their youth were two and a half times more likely to develop an increase in pigments found in the retina.
No relationships were found between UVB exposure, winter leisure time spent outdoors, skin sun sensitivity, or the number of bad sunburns experienced by the time the study began and the 10-year risk of abnormal blood vessel formation or plaque deposits in the retina.