The findings suggest that people who take aspirin for primary heart disease prevention should consider periodic blood work for anemia and low iron.
People who take a daily low-dose aspirin may be more likely to develop anemia, according to a new study published on June 20 in the Annals of Internal Medicine. Researchers found that prolonged daily aspirin use increased the risk of anemia by 20 percent in people who were mostly age 70 or older.
Importantly, these findings were in people who didn’t have any evidence of bleeding in their gastrointestinal (GI) tract, which is where you might expect bleeding from aspirin to occur, says a coauthor of the study, Harvey Cohen, MD, a professor of medicine at the Duke University School of Medicine in Durham, North Carolina.
“It’s still likely that the anemia was caused by bleeding, it’s just subclinical, or not severe enough to be readily observable. That suggests that people who are receiving low-dose aspirin should be monitored for the potential of iron deficiency, even when they don’t have obvious bleeding,” Dr. Cohen says.
Study Shows ‘Hidden’ Blood Loss Due to Daily Aspirin
This is the first large-scale study to look at long-term negative effects of aspirin, says Rachael McGuirk, MD, a family medicine physician at the Ohio State University Wexner Medical Center in Columbus, who was not involved in the research.
“While we already know that aspirin can cause serious bleeding problems requiring hospitalization in some people, this study shows that there can be ‘hidden’ blood loss in those who take daily aspirin, too. Over the years, people who take aspirin can lose small amounts of blood in their stool from stomach irritation,” she says.
100 Milligrams of Aspirin Increases Likelihood of Anemia and Bleeding Events
Researchers analyzed data from about 18,000 initially healthy older adults in Australia and the United States, a sub-analysis of the randomized ASPREE (Aspirin in Reducing Events in the Elderly) trial, the first trial to show that aspirin did not prolong healthy life span in initially healthy older individuals, mostly age 70 and older.
Over a median of 4.7 years, the incidence of anemia was 51.2 events per 1,000 person-years in the group who took 100 milligrams (mg) of aspirin each day, compared with 42.9 events per 1,000 person-years in the placebo group, or those who took a sham pill instead of aspirin.
The estimated probability that a participant would develop anemia within five years was 23.5 percent for the group taking aspirin, compared with 20.3 percent in the placebo group.
People taking aspirin were also more likely to have a clinically significant bleeding event; 3 percent of the aspirin group experienced at least one event, compared with 2.1 percent of those in the placebo group.
In Older Adults, Anemia Is Linked to Cognition Problems and Depression
There are three types of anemia; the type of anemia observed in this trial appears to be largely iron deficiency anemia, says Cohen.
As the name suggests, iron deficiency anemia is due to insufficient iron, according to Johns Hopkins Medicine. Without enough iron, the body can’t produce enough hemoglobin, a substance in red blood cells that enables them to carry oxygen. Loss of blood from things like GI bleeding, injury, and menstrual bleeding can cause this type of anemia.
The incidence of anemia is known to increase with age — estimates suggest about 10 percent of adults ages 65 and up are anemic, with a higher prevalence among people in nursing homes and hospitals. By age 85 and older, 39.5 percent of men and 21.9 percent of women have anemia, according to the Centers for Disease Control and Prevention (CDC).
In older adults, anemia is associated with functional decline, increased fatigue, disabilities, depressive symptoms, and cognition problems, according to the National Institutes of Health (NIH).
What Are the Current Guidelines for Aspirin?
The participants in this trial were taking aspirin for primary prevention of heart disease, and it should be noted that a daily low-dose aspirin is no longer recommended for primary prevention, though it’s still recommended for secondary prevention, says Cohen.
“But despite that, there are actually still a substantial number of people who are taking aspirin for primary prevention. I think these findings are perhaps another indication of why it might pay to be more cautious in encouraging people to use low-dose aspirin in primary prevention, because here’s yet another potential downside to doing so,” he says.
Primary prevention recommendations are intended to prevent the first occurrence of a heart attack, stroke, or a cardiovascular disease event, whereas secondary prevention of cardiovascular disease is meant to prevent recurrent events in people who have already had a heart attack, stroke, or coronary revascularization procedure (like a stent or a bypass surgery).
In 2022, the U.S. Preventive Services Task Force (USPSTF) recommended against starting low-dose aspirin for the primary prevention of cardiovascular disease in people 60 or older, making recommendations in line with other national organizations, such as the American Heart Association (AHA).
The update was based on mounting evidence of potentially fatal internal bleeding that can result from regular aspirin use, suggesting the risks may be greater than the preventive benefits.
The recommendations apply only to the primary prevention group; they don’t apply in any way to people who already have established cardiovascular disease, according to the statement.
Experts agree that you should not take daily low-dose aspirin without talking to your doctor; if you are taking low-dose aspirin for secondary prevention of heart disease, do not stop taking it.
Should You Talk With Your Doctor if You Are Taking Daily Aspirin?
“I think that absolutely, a discussion is warranted about the risks and benefits of taking daily aspirin. In the case of secondary prevention, there is a more substantial weight on the balance side of taking low-dose aspirin, but I think people need to understand that there are still potential downsides as well,” says Cohen.
“In the last few years, primary care doctors have not been recommending daily aspirin as much as they used to. While aspirin is a very important medication for some people, it can cause more harm than benefit in others,” says McGuirk.
What are the considerations when making the decision? Aspirin can help prevent clots from forming in blood vessels such as in the brain, heart, or legs, says McGuirk. “If someone has had a heart attack or stroke before, medications like aspirin are necessary to help prevent it from happening again,” she says.
Aspirin might also be beneficial in those who are at a higher risk of future heart attack, such as people with diabetes, smokers, or those with an extensive family history of heart disease, says McGuirk.
“However, aspirin might not be appropriate in those who have a high risk of bleeding. It is important to talk to your doctor about whether aspirin is right for you. Your doctor can weigh the benefits and risks of aspirin as it relates to your individual health,” she says.
Recommendations for Older Adults Who Take Daily Aspirin
“If someone does need to take daily aspirin, they should talk to their doctor about how to get an iron-rich diet. They should also consider limiting the use of other substances that can irritate the stomach, such as alcohol or NSAIDS like ibuprofen and naproxen,” says McGuirk.
Tests for anemia or low iron in adults without a clear reason isn’t the current standard of care, but this latest study raises the question of whether those who take aspirin should get periodic blood work for anemia and low iron, says McGuirk. “People who are on long-term aspirin should consider asking their doctor if they should be screened for anemia or low iron,” she says.
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