People who take aspirin regularly over the long-term have a higher risk of developing age-related macular degeneration (AMD), the main cause of blindness among seniors, researchers from the University of Sydney, Australia, reported in JAMA Internal Medicine.

Aspirin is commonly taken by patients to protect from cardiovascular disease, including ischemic stroke and heart attack (myocardial infarction). It is one of the most widely used drugs worldwide.

A recent study pointed towards a link between AMD and regular aspirin usage, especially the more visually damaging neovascular (wet) form. However, other studies have come out with conflicting findings. As background information, the authors added that smoking is also a major preventable risk factor for AMD.

Gerald Liew, Ph.D. and team set out to determine whether regular aspirin use was linked to a greater risk of developing AMD. They carried out a prospective analysis of information from an Australian study which examined 2,389 participants over a fifteen year period. 10.8% (257 individuals) of them were regular aspirin users.

Fifteen years later, after follow-up, the team found that 63 of the study group had developed incident neovascular AMD.

The researchers wrote:

“The cumulative incidence of neovascular AMD among nonregular aspirin users was 0.8 percent at five years, 1.6 percent at 10 years, and 3.7 percent at 15 years; among regular aspirin users, the cumulative incidence was 1.9 percent at five years, 7 percent at 10 years and 9.3 percent at 15 years, respectively. Regular aspirin use was significantly associated with an increased incidence of neovascular AMD.”

Any decisions on whether to carry on or stop aspirin therapy have to be made on an individual basis, the authors emphasized. There is not enough clinical evidence to advise doctors to change clinical practice, they added. Perhaps patients with a very high risk of developing neovascular AMD, for example, those with existing late AMD in the other fellow eye, for whom the risk of incident neovascular AMD might be slightly higher, should be re-evaluated.

George A. Diamond, M.D. and Sanjay Kaul, M.D., of Cedars-Sinai Medical Center, Los Angeles, in an invited Commentary wrote that the study had strengths and limitations. “It provides evidence from the largest prospective cohort with more than five years of longitudinal evaluation reported to date using objective and standardized ascertainment of AMD.

The main limitation of the study was its non-randomized design which contained the potential for residual confounding “that cannot be mitigated by multivariate logistic regression or propensity score analysis.”

From a science-of-medicine point of view, the evidence was not compelling enough to be clinically directive, they added. The “hypothesis-generated findings” need to be backed up with prospective randomized studies before any recommendations on patient behavior or clinical practice can be made.

From an art-of-medicine point of view, however, some courses of action are available to the thoughtful doctor, based on the limited amount of available evidence. “In the absence of definitive evidence regarding whether limiting aspirin exposure mitigates AMD risk, one obvious course of action is to maintain the status quo.”

Macular degeneration is a an eye disease in which patients gradually lose their central vision – things that are directly in front of them become progressively harder to see. People with macular degeneration find it much harder to write, read, recognize faces, and drive.

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Two boys seen by somebody with normal vision

The macula lutea is a yellow, oval-shaped spot near the center of the retina, in the eye. Macular degeneration is caused by retinal damage. It mainly affects elderly individuals.

In developed nations, macular degeneration is the major cause of partial blindness among patients aged fifty or more years. The patient can usually perform other activities in daily life, because even though their central vision is affected, there is still enough peripheral vision.

There are two forms of macular degeneration:

  • Dry macular degeneration – this progressive disease develops slowly, gradually over time. No treatment is available. There are things the person can learn to cope with the disease.
  • Wet macular degeneration – symptoms develop much more rapidly. As soon as symptoms become apparent the patient should be treated straight away. Wet macular degeneration is much more serious than the dry form.

Researchers from the Singapore Eye Research Institute at the National University of Singapore reported in The Lancet (May 2012 issue) that age-related macular degeneration is set to become much more common as people live longer. Currently, about one in every five individuals aged 60 years or more has AMD.

Written by Christian Nordqvist