A Test of Risk for AMD?

Summarized by Robert W. Griffith, MD
March 12, 2004

Introduction

Age-related macular degeneration (AMD) is a serious problem for the elderly; it leads to blindness, and in many cases it can't be treated. The best option, obviously, is prevention. This involves knowing the possible risk factors, and addressing them. Accepted risk factors are: cigarette smoking, nutritional deficiencies, obesity, and high blood lipid levels.

You can see that many of these risk factors are the same as those for cardiovascular disease. It therefore seemed obvious to a group of Boston researchers to see if increased blood C-reactive protein (CRP) levels could 'predict' the likelihood of AMD in the same way that it predicts cardiovascular disease. This led to a clinical study that has now been reported in the Journal of the American Medical Association.

What was done

Eleven clinical centers in the USA are participating in the Age-Related Eye Disease Study (AREDS), which is exploring the effects of antioxidant vitamins and minerals on AMD and cataracts. Two of these centers in the Boston area provided 930 patients for this study, who had been enrolled between 1993 and 1998. There were 183 persons without any disease of the macula, 200 with mild changes, 325 with moderate changes, and 220 with advanced AMD. Their average age was 69 years (range 55 to 80).

Questionnaires were used to determine the presence of risk factors for AMD. Blood samples taken in 1996 and 1997 were analyzed for CRP levels. Then statistical analyses were done to look for links between the degrees of AMD and the CRP levels.

What was found

The CRP levels were significantly higher in those patients with advanced AMD than in those with no macular changes; the average was 3.4 mg/L in the AMD patients, and 2.7 mg/L in the normal participants.

After making adjustments to allow for different ages, smoking status, body weight, and so on, it was found that increased CRP levels were associated with moderate and advanced AMD. People with the highest CRP levels were roughly twice as likely to have AMD as those with the lowest CRP levels. This association was seen in both smokers and non-smokers.

What does this mean?

This study shows that raised CRP levels are a risk factor for developing AMD. It's an important finding, as it suggests that inflammation is a possible factor in how AMD occurs (as is the case with cardiovascular disease). Knowledge of this sort will help researchers find ways to prevent the development of this distressing condition. And perhaps anti-inflammatory drugs may one day be shown to be helpful as preventative medication?

In the meantime, those older people who are worried about the risk of getting AMD should stop smoking, eat plenty of vitamin-rich fruits and vegetables, control their weight, and keep a low cholesterol level. And go for regular eye exams!

Source

• Association between C-reactive protein and age-related macular degeneration. JM. Seddon, G. Gensler, RC. Milton,  et al., JAMA, 2004, vol. 291, pp. 704--710

Related Links
Age-Related Macular Degeneration (AMD) - An Overview
Supplements May Be a Boost to Older Eyes
Low-Fat Diet May Help Protect Eye Health

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