Health After 50
The Eye-Heart Connection
More than 20 years ago, the Framingham Heart and Eye Study uncovered an association between diabetic retinopathy and cardiovascular diseases, including coronary heart disease and stroke. Several European studies have noted the link as well. And some studies also found that as diabetic retinopathy worsens, the risk of cardiovascular disease mounts.
But several recent studies have honed in more closely on the details behind the connection. For example, researchers recently reported a strong association between diabetic retinopathy and the amount of calcium in the coronary arteries. Calcium levels are a reliable marker for atherosclerosis, which can lead to stroke, heart attack, and, yes, eye problems. Atherosclerosis is the hardening and narrowing of arteries from plaque, a buildup on blood vessel walls of cholesterol but also of calcium and other substances.
For the study, which was reported in Diabetes Care, investigators used computed tomography to detect the level of calcium in each of four spots in the coronary arteries in 204 people with type 2 diabetes. They found that those with proliferative diabetic retinopathy (the dangerous growth of new blood vessels on the back of the vitreous humor) were six times more likely to have coronary artery calcium (CAC) levels over 400 -- a score that places them at risk for heart disease -- than people who didn't have the condition. The median CAC score among those with proliferative diabetic retinopathy was 981. For people who did not have proliferative diabetic retinopathy, the median CAC score was 197.
The researchers also found that when they accounted for other risk factors for heart disease, such as age, low levels of the "good" cholesterol, high-density lipoprotein (HDL), high triglyceride levels, prior heart-related illnesses, weight, smoking, and high blood pressure, the association between diabetic retinopathy and calcium levels persisted.
Taken together, these findings suggest that increased CAC levels are an independent risk factor for diabetic retinopathy and that both may be caused by the same underlying pathology. Pathologies implicated in the development of diabetic retinopathy include the accumulation of sugars, damage to cells by free radicals, bonding of sugar with protein molecules, stimulation of certain biological pathways, and increased levels of certain growth factors -- all of which have been associated with the development of atherosclerosis.
Posted in Vision on November 19, 2010
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