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To the Editor It is unfortunate that the study by Liew and colleagues1 did not quantify the actual milligram dose of aspirin that was taken by each subject, but rather only the amount of time each subject took aspirin at any dose. The authors stated that aspirin is usually prescribed at a dose of 150 mg/d in Australia, which is an odd dose in that it is probably too small for effective analgesia in most patients, but larger than the minimum dose required for steady-state inhibition of platelet aggregation to reduce cardiovascular thrombosis.2 The “dose-response effect” that the authors found refers to the “time dose” or cumulative amount of time the patient took aspirin (at any milligram dose). It would be useful to know in addition whether there is a milligram dose-response effect for risks associated with daily aspirin use. Such an effect might be continuous or a “threshold effect,” such that aspirin below a certain dose, taken daily, might have no adverse effect. Most aspirin prescriptions in the United States are written for the lowest dose available, 81 mg, and are prescribed for the purpose of platelet inhibition, not analgesia.3 The physicians who write these prescriptions would be more interested in knowing whether an aspirin dose of 81 mg/d is associated with increased risk of age-related macular degeneration, rather than the less-commonly prescribed dose of 150 mg.
Keller DL. Is 81-mg Aspirin Associated With Age-Related Macular Degeneration Risk?. JAMA Intern Med. 2013;173(15):1476. doi:10.1001/jamainternmed.2013.8147