Age-related macular degeneration is a progressive and sight-threatening disease affecting the central area of the retina at the back of the eye. There are Cochrane Reviews of the use of antioxidant vitamin and mineral supplements to prevent or slow down progression of the disease and the latter was updated in September 2023. Here's lead author, Jenny Evans from the London School of Hygiene and Tropical Medicine in the UK to tell us about the latest evidence.
Mike: Hello, I'm Mike Clarke, Podcast Editor of the Cochrane Library. Age-related macular degeneration is a progressive and sight-threatening disease affecting the central area of the retina at the back of the eye. There are Cochrane Reviews of the use of antioxidant vitamin and mineral supplements to prevent or slow down progression of the disease and the latter was updated in September 2023. Here's lead author, Jenny Evans from the London School of Hygiene and Tropical Medicine in the UK to tell us about the latest evidence.
Jenny: Age-related macular degeneration, or AMD, affects many people across the world. Approximately, one in three people over 80 years of age have early signs of the disease.
One theory as to why AMD develops relates to “oxidative stress” in the retina, which means that taking anti-oxidants such as vitamin C and E, carotenoids and zinc might help. Our pair of Cochrane Reviews examine whether antioxidant vitamins and mineral supplements, can prevent the development of AMD or slow down its progression.
Our update of the review of whether these slow down the progression of AMD now includes 26 studies. These tested various types of vitamins against placebo or no treatment in people with AMD. The evidence was mixed with, in general, the studies being small, and of short duration with patients being followed for less than two years. However, one large study from the USA, called the Age-related Eye Disease Study or AREDS assessed patients over 5 years and still dominates the review, finding that a combination of vitamin C, E, carotenoids, and zinc may slow AMD progression.
The data from AREDS suggest that there would be approximately four fewer cases of progression to late AMD for every 1000 people with very early signs of AMD, who are at low risk of progression, if they take the combination of vitamins used in that trial. In people who already have intermediate AMD and are, therefore, at higher risk of progression this benefit would rise to approximately 80 fewer cases of progression for every 1000 people taking the vitamins. However, it's important to note that the carotenoid used in AREDS was beta-carotene and there are concerns about its safety in people who smoke. A later study, by the same investigators, suggested that beta-carotene could be replaced by lutein and zeaxanthin.
In regard to side effects, vitamin supplements are generally regarded as safe but there was limited information from these studies on harms. However, evidence from other Cochrane Reviews suggests that mortality in people who take vitamins is generally similar compared with people who do not, with the exception of vitamin E and beta-carotene which are associated with a small increased risk of mortality.
Turning to our review of the use of antioxidants to prevent AMD, we haven't updated it at this time because there have been no new studies since our last version in 2017. The review includes five large studies that compared taking vitamin E, beta-carotene, vitamin C and multivitamin with taking a placebo in people in the general population who did not have AMD. More than 75,000 people were randomised in these studies. They were followed for 4 to 10 years, and people taking the supplements were found to have a similar chance of developing AMD compared with people not taking the supplements.
In summary, therefore, our pair of reviews show that taking a combination of antioxidant vitamins, as used in AREDS, may slow down the progression of the disease in people with a diagnosis of AMD, but that vitamin supplements (vitamin C, E or beta-carotene) are unlikely to prevent the development of AMD.
Mike: If you would like to read more about AREDS and the other studies in Jenny's reviews, you can find both online at Cochrane Library dot com with a simple search for 'antioxidants for AMD'.