To cut your risks of age-related macular degeneration (AMD), 'go fish'!

Summarized by Robert W. Griffith, MD
July 12, 2000 (Reviewed: December 11, 2002)

Age-related macular degeneration (AMD) is a leading cause of vision loss in older persons. Several studies have been done to determine what possible risk factors there may be. So far, the ones that are recognized include high blood pressure, heart disease, increased weight (body mass index = BMI), cigarette smoking and the amount of antioxidants in the body. Of course, there is a tendency for AMD to run in families, and to occur in people with light eyes, or lens opacities. The study summarized here has been done to examine the association between high blood pressure and two types of AMD -- the neovascular and the non-neovascular forms.

The study was done by comparing people from ophthalmic practices in the New York area that had AMD with people without the condition who were attending the practices for other reasons (e.g. routine eye exams).

Photographs of the back of the eye (the fundus) were taken, and the participants were questioned about their dietary habits, their medical history (stressing blood pressure and heart conditions), medications, smoking and alcohol use. Blood samples were taken for lipid analyses.

The subjects were classified into neovascular AMD (182), non-neovascular AMD (227), and those without any AMD (235). The average age of those with the neovascular AMD was slightly greater than those with no AMD at all -- 71 years versus 68.5 years. The majority of them (60%) were women. In general, those with neovascular AMD had less years of formal education and were more likely to be blue-collar workers than those from the other two groups. These minor changes were adjusted for in the analyses of results.

Blood pressure measurements were similar in the three groups, but people with a diastolic pressure above 95 mmHg (the lower reading) or a formal diagnosis of high blood pressure were more likely to have neovascular AMD than people with normal blood pressure. The same was true for increased dietary intake of cholesterol and raised high-density lipoprotein levels.

This study shows, therefore, an increased risk of neovascular AMD for people with moderate to severe high blood pressure, but there was no such association with non-neovascular AMD; this suggests to the authors of the study that there may be differences in the causation of the two types of AMD. They go further and suggest that neovascular AMD and high blood pressure have a similar underlying cause.

Support for this comes from a new Australian study, which has examined possible links between diet and the occurrence of AMD. Over 3,500 people aged 49 and above had their eyes examined for AMD, and completed a food questionnaire that allowed calculation of their intake of dietary fat and fish.

After adjusting for age, sex, smoking, and a family history of AMD, it was found that more frequent consumption of fish appeared to protect against late, or advanced, AMD. Eating fish more than once a week halved the risk compared with those who ate fish less than once per month. As in the first study, those people with a high cholesterol intake were significantly more likely to develop AMD, whereas a high intake of polyunsaturated fat was associated with a lessened likelihood of AMD (roughly equal to eating fish more than once a week).
It is clear that people who are inherently at risk of developing AMD (those with a family history and light eye color) can do something about it - they can stop smoking, cut their alcohol intake, reduce all their heart disease risk factors, take vitamin E, and increase their omega-3 fatty acid intake, which is easiest done by eating more fish!

Source

• Hypertension, cardiovascular disease, and age-related macular degeneration. L. Hyman, AP.  Schachat, Q. He,   et al., Arch Ophthalmol, 2000, vol. 118, pp. 351--358

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