REVIEW QUESTION

Does the use of antioxidant vitamin and mineral supplements prevent the development of age-related macular degeneration (AMD)?

TYPE OF REVIEW

This is a systematic review of five studies comparing antioxidant supplements with placebo in the development of any and/or late AMD.

RELEVANCE FOR NURSING

In high income countries with aging populations, age-related macular degeneration (AMD) is the leading cause of blindness and visual impairment. AMD is a condition that affects the central area of the retina (macula), and a person in the early stages of the disease is usually asymptomatic. As AMD progresses, there may be disruptions in the retinal pigment epithelium, leading to hypo- and hyperpigmentation. In the advanced stages of the disease, atrophy of this pigmented cell layer and, in some patients, development of new blood vessels beneath it lead to the death of photoreceptors and central vision loss.

The photoreceptors in the retina are vulnerable to oxidative stress because of exposure to oxygen and light. Antioxidants may be beneficial in treating AMD by delaying or inhibiting cellular damage in the retina through scavenging of free radicals produced in the process of light absorption. The association of AMD and antioxidant micronutrients has been examined in observational studies; however, the investigation of purposeful supplementation is limited and observational study results have been inconclusive. Furthermore, with the increased promotion of antioxidant vitamin and mineral supplementation for age-related eye disease, the current evidence requires closer consideration.

CHARACTERISTICS OF THE EVIDENCE

Five studies with a total of 76,756 participants from Australia, Finland, and the United States were included in the review. Three studies recruited men only, one recruited women only, and one recruited both; the age range was 40 to 84 years. The duration of supplementation ranged from four to 12 years, and studies investigated vitamins C and E, beta carotene, and multivitamin supplements compared with placebo. All studies reported on the primary outcome of the development of any AMD and/or late AMD.

Studies comparing vitamin E and placebo found that vitamin E supplements do not prevent the development of any AMD (high-certainty evidence) and there was only a slightly increased risk of developing late AMD (moderate-certainty evidence). Two studies that recruited male participants and only reported on the comparison of beta carotene and placebo found that beta carotene did not prevent any AMD (high-certainty evidence) or late AMD (moderate-certainty evidence). One study that reported on vitamin C versus placebo and a multivitamin versus placebo suggested that vitamin C supplementation did not prevent any AMD (high-certainty evidence) or late AMD (moderate-certainty evidence); in the multivitamin group, there was a slightly increased risk of any AMD (moderate-certainty evidence) and of late AMD (moderate-certainty evidence).

BEST PRACTICE RECOMMENDATIONS

There is currently no evidence that vitamin C or E, beta carotene, or multivitamin supplementation prevents or delays the onset of AMD in people without an AMD diagnosis.

RESEARCH RECOMMENDATIONS

Research should continue to evaluate whether antioxidant vitamin and mineral supplementation prevents the development of AMD. As the evidence is unclear regarding a relationship between the intervention and the participants' age, it may be that the trials in this review were conducted too late and the period of supplementation was too short to demonstrate an effect. Potential interactions with risk factors for AMD and genetics also requires further investigation.

REFERENCE