People with age-related macular degeneration, a leading cause of severe vision loss, have double the usual risk of dying from a heart attack or stroke, Australian researchers reported on Thursday.
They found that for people under the age of 75 when the study began, those who developed early age-related macular degeneration had twice the risk of dying from a heart attack or stroke within the next decade.
People with the late stage of the incurable disease at the start of the study had five times the risk of dying from a heart attack, and 10 times the risk of dying from a stroke, Paul Mitchell of the Centre for Vision Research at the University of Sydney and colleagues found.
"However, our finding that late age-related macular degeneration predicts stroke or cardiovascular mortality was based on relatively small numbers and should be interpreted cautiously," they wrote.
The researchers, who reported their findings in the British Journal of Ophthalmology, studied more than 3,000 people all older than 49 years old at the beginning of the study between 1992 and 1994.
Over the following 10 years, the researchers conducted two general health and eye exams five years apart that included physical checks and photographs of the retina.
Age-related macular degeneration is a chronic disease that affects the central part of the retina of the eye, resulting in blurred central vision or a blind spot in the centre of one's visual field.
It does not affect peripheral vision, but the loss of clear central vision can rob a person of the ability to read, drive and recognize people's faces even without causing total blindness.
The researchers do not know what is actually triggering the elevated risk but said one explanation may be that the eye disease is simply a sign of older age when people are more prone to heart attacks and strokes.
The findings could also have important implications for doctors because of concerns that some current treatments for the eye disease may increase stroke risk, the researchers said.