Aspirin and Age-Related Macular Degeneration
Aspirin (acetylsalicylic acid) is one of the most widely used medications, with an estimated 40,000 tons consumed annually. Aspirin is taken for its analgesic, antipyretic, and anti-inflammatory effects. First isolated in 1897 from plant extracts (willow bark and spiraea, which contain salicylic acid), aspirin has been used to alleviate headache, pain, and fever for thousands of years. Indeed, Hippocrates described using willow bark powder for such symptoms.
More recently, elucidation of the mechanism of action of aspirin led to a Nobel Prize in 1982. Aspirin achieves its primary pharmacologic effects through irreversible inhibition of cyclooxygenase (COX), both the COX-1 and COX-2 variants, thereby inhibiting production of prostaglandins and thromboxanes.
Because of its antiplatelet effect, aspirin plays an important role in medical practice. It is used widely for cardiovascular conditions and has been shown to reduce the risk for cardiovascular events, such as stroke, and the risk for coronary events in some circumstances. Aspirin might also protect against some forms of cancer.
Despite its multitude of benefits, aspirin has recently come under fire again because of an association with age-related macular degeneration (AMD). AMD is a leading cause of vision loss in adults in the developed world. Most severe visual loss is associated with the neovascular (wet) form of AMD, and approximately 200,000 new diagnoses are made each year in the United States. Wet AMD is characterized by pathologic angiogenesis with abnormal growth of blood vessels under and into the neurosensory retina. These immature blood vessels can rupture and hemorrhage, a potentially devastating event for the retina in terms of visual function.
Because aspirin use and AMD are both common, a potential association between the 2 has been considered in many studies. Two major approaches have been used to study this association: prospective randomized trials and observational trials.