If you take daily low-dose aspirin under a doctor’s guidance, it’s a good idea to get tested regularly for anemia. According to a new analysis of data from a large, randomized controlled trial, published in the Annals of Internal Medicine in July, aspirin therapy increases the risk of anemia—defined as an abnormally low hemoglobin count—in older people. Hemoglobin is the key component of red blood cells that supply oxygen to tissues throughout the body.
At even the lowest doses, aspirin inhibits the ability of platelets in the blood to stick together and form clots—and millions of people in the U.S. take this inexpensive drug daily in hopes of preventing heart attacks and strokes, though such benefits have come under increased scrutiny in recent years.
For the study, researchers at Monash University in Australia randomly assigned more than 19,000 healthy older people in the U.S. and Australia—most white and over age 70—to receive either low-dose aspirin (100 milligrams) or a placebo daily. Participants had no prior history of heart attack or stroke and were not at increased risk for bleeding disorders or previously diagnosed with anemia.
After a median of 4.7 years, those who took aspirin were 20 percent more likely to have experienced anemia. Hemoglobin, which was measured annually, declined more steeply in the aspirin group than in the placebo group. In addition, levels of ferritin—the blood protein that stores iron used to help replenish hemoglobin—were markedly lower in the aspirin versus placebo group at year three. However, the absolute number of people affected was very small overall.
Anemia affects about one in 10 Americans by age 65 and more than four in 10 ages 80 and older. One of the most common causes is iron deficiency from blood loss, which, particularly in older people, may occur in the gastrointestinal tract as a result of aspirin therapy. Signs and symptoms include fatigue, headaches, depressed mood, and even overall cognitive decline.
The new analysis was based on data from the ASPREE (Aspirin in Reducing Events in the Elderly) study that was published in 2018 and found no evidence that low-dose aspirin led to a longer, disability-free life or headed off long-term cognitive decline. More recently, another study using data from ASPREE, published in JAMA Network Open in July, found that low-dose aspirin did not significantly decrease the risk of ischemic strokes (those caused by blood clots) and in fact increased the risk of bleeding in the brain. (The researchers did not evaluate aspirin’s effect on heart attacks in this analysis.)
The U.S. Preventive Services Task Force recommends that use of low-dose aspirin should largely be limited to those who have already had a heart attack or ischemic stroke (secondary prevention). Most other people without multiple risk factors for cardiovascular disease should not start aspirin therapy for prevention of a first heart attack or stroke because of increased risk of bleeding (gastrointestinal bleeding, intracranial hemorrhage, and hemorrhagic stroke). The new findings suggest that periodic monitoring of hemoglobin as part of a complete blood count (CBC) test should be considered to assess possible bleeding in older persons on aspirin.
