During the past month, I’ve been bombarded with newsfeeds proclaiming, “Aspirin Is Proven to Cause Macular Degeneration!” or some variation thereof.
However, as I investigated, I discovered that these headlines tended to overstate the certainty of the study’s findings and create a sense of alarm regarding aspirin and macular degeneration. So let’s take a factual look at the study, along with an interpretation of the study’s findings.
The study in question, entitled Associations between Aspirin Use and Aging Macula Disorder: The European Eye Study, has been published online ahead-of-print in Ophthalmology, the official journal of the American Academy of Ophthalmology. (Translation: Aging Macula Disorder = age-related macular degeneration, or AMD.)
Ophthalmology publishes original, peer-reviewed reports of research in ophthalmology, including new diagnostic and surgical techniques, treatment methods, the latest drug findings, results of clinical trials, and research findings.
The international authors are Paulus T.V.M. de Jong, MD, PhD; Usha Chakravarthy, MD, PhD; Mati Rahu, PhD; Johan Seland, MD; Gisele Soubrane, MD, PhD; Fotis Topouzis, MD; Johannes R. Vingerling, MD, PhD; Jesus Vioque, PhD; Ian Young, MD; and Astrid E. Fletcher, PhD.
About the Study: the Basics
Information from this study was presented initially at The Macula Society Annual Meeting, Tucson, Arizona; and the Association for Research in Vision and Ophthalmology Annual Meeting, Fort Lauderdale, Florida. Thus, many professionals have had the opportunity to learn about the study and its implications.
The purpose of the European Eye Study was to examine a potential association between aspirin use and early and late-stage AMD.
The study was a cross-sectional analysis that included 4,691 subjects, aged 65 years or older, from the national population registers of seven European countries.
A cross-sectional study involves an analysis of a population of subjects at one specific point in time (rather than studied over a longer period of time), which is important when evaluating the results of this particular study.
The Study Subjects
Participants were interviewed via a structured questionnaire that asked about aspirin intake along with other factors, including socioeconomic background, medical history, smoking, and alcohol consumption.
Aspirin intake was divided into four categories, ranging from “never take” to “daily use.” Participants were given standard tests for AMD, with their AMD progression graded using a five-stage scale.
A score of “0” indicated no AMD and the last stage – stage 4 – was also classified as being either dry or wet, since not all individuals with late-stage AMD progress to the wet form.
The Study Results
36.4% of the participants had early AMD (stages 0–3) and 3.3% had late AMD (stage 4). 41.2% reported monthly aspirin use, 7% reported at least once weekly use, and 17.3% reported daily use.
The researchers then calculated the associations between daily aspirin use and each grade/stage of AMD:
- a 26% increased risk of grade 1 AMD
- a 42% increased risk of grade 2 AMD
- no increased risk of grade 3 AMD
- a more than double risk of grade 4 wet AMD
- no increased risk of grade 4 dry AMD
In addition, the study was limited by the unknown amount/dosage of aspirin taken, as well as the possibility that participants may have taken aspirin after experiencing visual problems.
The Study Conclusions
The researchers conclude that frequent aspirin showed an association, research-wise, with early AMD and wet late AMD. They consider the possibility that aspirin affects blood vessels in the eye, since aspirin acts on the body in a variety of ways.
However, larger studies that follow people over time (as opposed to a cross-sectional study) and document their aspirin use and vision status will help resolve aspirin’s role in macular degeneration.
The Big Question: How To Interpret the Study Findings?
A number of resources and commentators have addressed the study findings.
From NHS Choices, part of the National Health Service (NHS) in the UK:
As this study assessed AMD and aspirin use at the same time, it cannot show that regular aspirin use causes or increases the risk of vision problems. As such, we cannot tell whether aspirin use or vision problems came first. On the evidence provided by this particular study, it is not possible to tell how or whether the two are related, or if some unaccounted for factor is linked to both aspirin use and AMD.
…this type of study cannot tell us if taking daily aspirin actually causes AMD. It can only show that the two things are linked and that twice as many people in the study who took an aspirin every day had AMD as people who never took any aspirin.
They were not able to rule out the possibility that patients who were prescribed daily aspirin for an illness – such as arthritis or heart disease – may have been more likely to have AMD because of the nature of their illness.
And finally, some words of wisdom from the Macular Degeneration Association:
Most seniors take aspirin to lower the risk of a stroke or heart disease by thinning the blood and preventing the formation of clots in the arteries that can lead to a stroke or a heart attack. One can see the problem with thinning the blood when the eye has wet macular degeneration.
If a patient does not have cardiac or blood clot problems that warrant blood thinning, a patient should think twice when popping that aspirin. My conclusion is that the saying “Take an aspirin and call me in the morning” should be replaced by the question “Is the heart risk greater than the blinding risk?”
VisionAware will provide updates on this important and ongoing research as they become available.
Sources: Reuters.com; OSN SuperSite; Macular Degeneration Association; NHS Choices; WebMD