No inverse relationship found between alcohol consumption and risk of macular degeneration

Moderate alcohol consumption was shown not to be protective for age-related macular degeneration.

ByBob Kronemyer

BOSTON — A prospective study among health care professionals concluded that moderate alcohol consumption is not protective for age-related macular degeneration (AMD), unlike for coronary heart disease.

“Our study really does not support the decrease in risk of AMD with moderate alcohol consumption,” said co-author Susan E. Hankinson, ScD, an associate professor of medicine at Harvard Medical School. “Entering the study, we thought perhaps there might be an inverse association because of one or two studies done in the past. An inverse association has been shown for heart disease. There also is the possible relationship between AMD and heart disease. But there has really not been sufficient data on the topic.”

The study, which was recently published in Archives of Ophthalmology, consisted of 32,764 female nurses and 29,488 male health professionals, all of whom were part of the Nurses’ Health Study and the Health Professionals Follow-up Study. Alcohol intake was assessed at baseline (between 1980 and 1994) and updated during follow-up evaluations using a validated semiquantitative food-frequency questionnaire. “After separate analyses for women and men, pooled estimates of the relationship of alcohol to the risk of AMD were calculated,” Dr. Hankinson said.

At baseline, 33% of women and 23% of men reported consuming alcohol never or less than once per month. In contrast, the majority in both cohorts reported consuming a low to moderate amount of alcohol (0.1 g/d to 14.9 g/d). Only 1% of women and 3.4% of men reported drinking 50 g or more daily. However, alcohol drinking (especially consumption of 30 g/d or more) was associated with smoking.

At the end of follow-up, AMD associated with a visual acuity loss of 20/30 or worse was diagnosed in 298 women and 153 men.

Heavy drinking

“We actually saw in a few subgroups a suggestion of an increase in AMD risk, but that is something I think needs to be followed up both by our study in a few years and by other studies,” Dr. Hankinson said. For instance, compared with non-drinkers, women who drank 30 g/d or more of alcohol had nearly double the risk of the disease in age-related analyses (relative risk 1.90). However, after controlling for smoking, the relative risk was reduced to 1.54. “Additional adjustment for other factors did not affect the relative risk,” Dr. Hankinson said. The same comparison among men indicated a positive but weaker association in age-adjusted analyses.

In addition, after controlling for age, smoking and other risk factors, alcohol intake of 30 g/d or more was associated with an increased risk of early and dry AMD in women (relative risk 2.04). This relationship among men, though, was much weaker (relative risk 1.18). In contrast, “there was no clear association between alcohol intake and wet AMD in either women or men,” Dr. Hankinson said.

Wine’s influence

The investigators examined the effect of three specific alcoholic beverages in relation to total AMD: beer, wine and liquor. A high intake of wine was positively related to AMD in both men and women. “The positive association that we had seen among the dry AMD seemed to be strongest when we looked at wine specifically,” Dr. Hankinson said. On the other hand, there was little affect from beer and liquor. “We don’t know why wine may have an influence, and beer and liquor do not,” she said.

Compared with non-drinkers, women in the highest category of wine intake (at least two drinks per day) had an age-adjusted relative risk of 2.20, which was only modestly attenuated after adjustment for smoking and other risk factors. Men had a 40% increased risk in the same wine category. The pooled multivariate relative risk for this comparison was 1.87, but by evaluating the “never” smokers separately, the pooled relative risk was reduced to 1.37. “This suggests possible residual confounding in the overall association,” Dr. Hankinson said.

At baseline, the results for red and white wine separately were only available for men. “The data suggests that the positive association was stronger — although not significant — for white wine,” Dr. Hankinson said. The multivariate relative risk for men who had two or more drinks of white wine daily was 2.16. However, “we had a very, very small number of cases, so this will need to be replicated in additional studies,” she said. Some of the women also were surveyed for type of wine. “As in men, women who consumed two or more drinks per day of white wine had a twofold increased risk,” Dr. Hankinson said.

Non-smokers

The investigators had good information for the most potentially important known confounders, including smoking and dietary intake. “Except for age and smoking, none of the other potential risk factors had a substantial influence on the associations,” Dr. Hankinson said. An analysis of only those who never smoked also showed only a modest change in the relative risk for total alcohol compared with everyone combined.

Despite the need for additional cohort follow-up and evaluation by additional studies, “I think it is important to recognize the strengths of this design,” Dr. Hankinson said. “One, it was prospective, which means we actually had information on alcohol intake prior to any diagnoses of eye disease.” Second, “we had a number of other risk factors, such as smoking and high blood pressure.” Third, “we had the large populations of men and women,” she said.

For Your Information:

Susan E. Hankinson, ScD, can be reached at Channing Laboratory, 181 Longwood Ave., Boston, MA 02115 U.S.A.; +(1) 617-525-2023; fax: +(1) 617-525-2008. The Alcohol Beverage Foundation provided partial support for this analysis.

Reference:

Cho E, Hankinson SE, Willett WC, et al. Prospective study of alcohol consumption and the risk of age-related macular degeneration. Arch Ophthalmol. 2000;118:681-688.