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How Do You Weigh the Benefits and Risks of Aspirin?

Before starting a daily regimen, carefully consider the benefits and risks of aspirin. Will you be helped or harmed by this amazing drug?

Aspirin has been around for over 100 years. Moreover, it is one of the most versatile drugs in the pharmacy. This tablet relieves pain, lowers fever and reduces inflammation. In addition, it has anti-platelet activity that makes it helpful against heart attacks in high-risk individuals. There has also been substantial research suggesting aspirin has anticancer activity. On the other hand, it can cause digestive tract irritation and even bleeding ulcers. These can be life-threatening. Scientists are still discovering how aspirin works (for example, see Handa et al, Free Radical Research, Dec. 2018). In addition, they are still uncovering some new benefits and risks of aspirin. As with so many things, some benefits (preventing blood clots) are linked directly to certain problems (excess bruising).

Low-Dose Aspirin Associated with Anemia:

Many people take low-dose aspirin every day to reduce their chance of a heart attack or stroke. Research shows, though, that people who take aspirin have a higher risk of serious bleeding.

Now, analysis of data from a placebo-controlled trial with nearly 20,000 volunteers shows that low-dose aspirin also increases the chance of anemia even when doctors do not detect significant bleeding. The trial is called Aspirin in Reducing Events in the Elderly, or ASPREE (Annals of Internal Medicine, June 20, 2023).

During almost five years of the study, the rate of anemia was 51 per 1,000 person-years in the group taking aspirin. In comparison, people in the placebo group had anemia detected at a rate of 43 per 1,000 person-years. That is an absolute difference of 8 per 1,000. The relative risk of anemia was nearly 20 percent greater among elderly people taking aspirin.

This suggests that older people should be cautious about taking aspirin on their own. If a doctor has prescribed aspirin following a heart attack or other event, however, they should not stop it. (Keep reading to learn more about this benefit.) Instead, a patient should ask the physician to monitor hemoglobin levels to make sure they don’t develop anemia.

Low-Dose Aspirin Led to Easy Bruising:

Q. Daily baby aspirin is not for everyone. My husband took it for a long time. In the last few years, we noticed that he gets large bruise marks on his hands. He has cut down to just one 81-mg aspirin tablet twice a week. He still gets bruises on his hands, but less frequently.

A. Doctors call this side effect “ecchymosis.” Other NSAIDs (ibuprofen, naproxen, etc) or anticoagulants can also lead to this kind of bruising. It makes sense to discuss your own potential benefits and risks of aspirin with your physician if you plan to take it regularly.

An Unexpected Hazard of Aspirin:

An epidemiological study demonstrated that men who take aspirin once a day have an increased risk for developing melanoma skin cancer (Orrell et al, Journal of the American Academy of Dermatology, Oct. 2018). The investigators examined records of nearly 200,000 individuals over five years. The absolute risk is small: 2.19 percent of people taking aspirin daily developed melanoma compared to 0.86 percent who did not take aspirin. Nonetheless, the relative risk is worrisome, as men taking aspirin were nearly twice as likely to develop this dangerous skin cancer (RR=1.87).

Women did not appear to have a higher risk of melanoma if they took aspirin. The researchers suggest that men who take aspirin every day should be cautious about sun exposure and get regular skin exams by a dermatologist. They do not recommend that men taking daily low-dose aspirin for cardiovascular protection stop taking the drug; they should merely increase their vigilance.

Aspirin and Skin Cancer:

This new finding is at odds with previous research. Years ago, we wrote about a report that aspirin could reduce the risk of skin cancer. Some of our readers reacted.

Q. I’ve been using aspirin to help prevent sunburn for years. I just read that aspirin can reduce the incidence of skin cancer. Is there a connection?

A. A decade ago a German study showed that people who took 250 mg of aspirin prior to sun exposure were less likely to burn (Photochemistry and Photobiology, Oct. 2001). Further research indicated that people who took aspirin were less likely to develop non-melanoma skin cancer (Oncology Letters, March 2015).

Another reader had an entirely different take on this research regarding the benefits and risks of aspirin.

A Skeptic on Aspirin to Prevent Sunburn:

Q. I recently read in your column that aspirin might reduce the effects of solar ultraviolet rays. I’m skeptical.

I take a full-strength aspirin every day because I don’t like the medications my cardiologist recommends. She doesn’t argue.

Despite that, I burn very easily. I also have skin cancer and a lot of pre-cancerous lesions. Those may be due, in part, to my misspent youth when I got absolutely broiled every year. Perhaps I am an exception, but people shouldn’t rely on aspirin to prevent sun damage.

A. There are a number of compounds that can reduce the risk of ultraviolet skin damage when taken orally. These include aspirin, blackberry extract and luteolin (Journal of Investigative Dermatology, Jan. 2021; Toxicology and Applied Pharmacology, Apr. 1, 2015; Molecular Medicine Reports, Sept. 2016). None of these will substitute for conscientious sunscreen use and common sense. Wearing protective clothing and staying out of the midday sun are the foundation of skin protection. That’s especially true for someone like you who is so sensitive to sun damage.

Benefits and Risks of Aspirin:

Aspirin is a household staple for lowering fever and treating pain. Beyond those uses, the best-known benefit of aspirin is probably its ability to reduce the chance of a heart attack or a stroke. In 2016, the US Preventive Services Task Force made a controversial recommendation with respect to aspirin for heart disease prevention.

Aspirin Pros & Cons:

For years, the evidence has shown that people who take aspirin lower their risk of heart attacks but increase their chances of bleeding ulcers or bleeding strokes. On the plus side, aspirin appears to reduce the risk of several different types of cancer, but some people are quite sensitive to aspirin and may develop nasal polyps or even anaphylactic reactions to the drug. Balancing the benefits and risks of aspirin can be complicated, and the Task Force made a rather complex recommendation (Annals of Internal Medicine, April 12, 2016 ).

Who Should Take Aspirin to Prevent a Heart Attack?

The USPSTF suggests that people in their 50s or 60s at high risk of heart disease might prevent a heart attack by taking aspirin, perhaps just one low-dose tablet a day. Younger people, older people, and those at very low risk of heart disease may not reap the anticipated rewards.  As a side benefit, however, those on a regular low-dose aspirin regimen to prevent a heart attack also lower their risk of colorectal cancer.

It might take many years for this effort to prevent a heart attack to pay off. People with a life expectancy less than ten years probably won’t benefit from taking aspirin, and those with bleeding disorders or a history of ulcers should avoid it.

Taking Aspirin During a Heart Attack:

People are often advised to take aspirin and call the ambulance when they feel that they may be experiencing a heart attack. One reader asked how to do that.

Q. You recently wrote about how to get aspirin into the system quickly in the event of a heart attack. Years ago my mother would give me Aspergum. Wouldn’t that work?

A. You are right that Aspergum was once a way to get aspirin (227 mg) into the body quickly. It is no longer available in the U.S.

Several readers brought a different product to our attention, however. UrgentRx makes a powdered aspirin (Ache + Pain Relief to Go) containing a 325 mg dose designed for rapid absorption with or without water.

The standard recommendation for those experiencing chest pain or other heart attack symptoms is to chew aspirin and wash it down with a glass of water after calling 911. You will find more information on the best way to take aspirin for a heart attack here.

Preventing Blood Clots with Aspirin:

Blood clots in veins can lead to life-threatening complications, including pulmonary embolism. Research from Australia suggests that aspirin could reduce the risk of recurrent venous thromboembolism or VTE (Circulation, online August 25, 2014).

People who have had one clot are at a substantial risk for developing another. These patients are treated with anticoagulant medications. Traditionally, they were put on warfarin, but newer-generation anticoagulants such as apixaban (Eliquis) are now becoming popular.

The trouble is that such drugs are pricey and pose a risk of serious bleeding. Australian investigators analyzed data from more than 1,200 patients who had experienced a serious blood clot. After the initial treatment with warfarin was discontinued, the subjects took 100 mg of coated Bayer aspirin or placebo daily. Aspirin cut the risk of a recurrence by about 40 percent without significantly increasing the risk of hemorrhage. The authors concluded that humble aspirin is a useful treatment against recurrent blood clots.

Aspirin May Be Helpful for a Long Flight:

Deep vein thrombosis, a blood clot in one of the large veins of the leg, is a dangerous condition. At one point about a decade ago, it was dubbed “economy-class syndrome” because people on long flights who can’t stretch out are at risk. Actually, anyone sitting still for hours could develop this complication, whether they sit in first class or economy, in a car or in front of a computer.

The danger from a DVT is that the clot could break loose and land in the lungs. There it forms a pulmonary embolism, which makes breathing difficult. Pulmonary embolism is potentially life threatening.

Will Hours on a Plane Lead to a Blood Clot?

Q. I will be traveling overseas soon and am worried about the effects of sitting for 10 hours on the plane. I have heard that aspirin might prevent a blood clot in my legs. Is this true?

A. If you don’t move your legs around, you could develop a blood clot. This can be a complication of surgery such as knee or hip replacement as well as of a long flight. Getting up every few hours and walking to the bathroom can be useful, if that is possible. To that end, you may wish to accept a beverage whenever a flight attendant offers one.

The Activity of Aspirin:

People who have experienced a blood clot in their legs (deep vein thrombosis or DVT) are more prone to another clot. Low-dose aspirin has been found to reduce the risk of recurrences (European Journal of Internal Medicine, Jan., 2014).

Aspirin can interact with a number of other medications, though. Ask your doctor whether aspirin would be safe with any other drugs you take.

 Lower Your Stroke Risk with Aspirin:

A sudden spell of dizziness, trouble walking or speaking, confusion or incoordination might signal a transient ischemic attack or TIA, even if it lasts for just a few minutes. Such a mini-stroke could be a red flag for a major stroke risk. Reducing the chance of a stroke should be part of the equation when considering benefits and risks of aspirin.

Aspirin and Stroke Risk:

A study that analyzed data from 12 clinical trials involving over 15,000 subjects suggests that aspirin can reduce the risk (Rothwell et al, The Lancet, July 23, 2016). People who took aspirin following their TIA were 60 percent less likely to have a stroke over the next six weeks than those who did not. The absolute risk was not as high as that might sound, however.

According to the researchers,

“84 of 8452 participants in the aspirin group had an ischaemic stroke vs 175 of 7326” in the control group.

Severe or fatal stroke risk was reduced even more. In the first two weeks after a TIA, 2 out of 6691 people taking aspirin had a disabling or fatal stroke compared to 23 of 5726 in the control group. That’s a reduction of more than 70 percent (relative risk). Although aspirin continued to keep the risk of a major stroke low for the next several weeks, there was no difference between the two groups after three months.

How Aspirin Might Help:

Aspirin helps to keep blood clots from forming and blocking a blood vessel in the brain. Anyone who notices sudden vision problems, weakness on one side or slurred speech should call 911 and take an aspirin, say the investigators, in advice similar to that for people experiencing symptoms of a heart attack.

Preventing Cancer with Aspirin:

A number of studies have shown that people who take aspirin on a regular basis are less likely to be diagnosed with certain cancers. This is one reader’s response:

Q. I am a participant in the NIEHS Sister Study because my younger sister had bilateral breast cancer in premenopause. I have long intuited that my use of aspirin for hip and knee arthritis has been protective. It makes me happy to learn that aspirin may indeed help prevent breast cancer.

Sister Study Finds Aspirin Helps Prevent Breast Cancer:

A. The Sister Study run by the National Institute of Environmental Health Sciences has recruited 50,000 women who have sisters with breast cancer. The goal is to determine which environmental and genetic factors could play a role in breast cancer in this high-risk group.

A report from this study was published in BMC Cancer (online, Dec. 16, 2015). It found that regular aspirin use reduced the risk of breast cancer among premenopausal women. It is heartening to have something women can do to try to prevent breast cancer.

Reducing the Chance of Metastasis:

Aspirin not only appears to reduce the risk of developing certain cancers (colorectal, esophageal, stomach and lung), it may also reduce the likelihood that cancer will spread (PLOS ONE, online, April 20, 2016).

Cancer Immunotherapy Treatment Benefits from Aspirin Boost:

Beyond helping prevent some cancers, aspirin also shows promise in conjunction with immunotherapy treatment. This may be important in calculating the benefits and risks of aspirin. In this approach, pricey new medications enhance the body’s own immune defenses to better fight cancer cells.

How Aspirin Could Help:

A surprising study in mice has revealed that giving aspirin along with some of the new high-tech treatments can turbo-charge their immune-boosting potential. Aspirin seems to be especially helpful for enhancing the effectiveness of an exciting class of drugs that inhibit a compound called PD-1 or programmed cell death protein-1.

How Aspirin Potentiates PD-1 Inhibitor Immunotherapy:

Aspirin appears to work by blocking prostaglandin E2. Cancer cells make large amounts of this compound to dampen immune system activity. So far, however, the exciting results in enhancing the effects of PD-1 inhibitors have been achieved only in mice (Cell, September 3, 2015).

Clinical trials will be needed to see if this preliminary research holds up in humans, but epidemiological research suggests that aspirin itself has anti-cancer action. Research from China, for example, showed that women who took aspirin on a regular basis were 50% less likely to be diagnosed with lung cancer (Lung Cancer, August 2012). In addition, researchers have long been aware that aspirin use reduces the likelihood of a lung cancer diagnosis (Annals of Internal Medicine, Sept. 1, 2015), even though regular aspirin intake can damage the stomach or small intestine. It seems that genetics can help determine whether aspirin is useful for colon cancer prevention (JAMA, March 17, 2015).

Different sorts of genetic profiles may come into play in the possible use of aspirin to turbo-charge the anti-PD-1 immunotherapy. A significant amount of research showing aspirin cuts cancer risks offers hope that human studies might demonstrate a helpful interaction between aspirin and the PD-1 inhibitors such as pembrolizumab (Keytruda) or nivolumab (Opdivo).

Aspirin has also been paired with metformin in research on overcoming prostate cancer.

Aspirin to Prevent Pre-eclampsia:

Even before scientists discovered aspirin’s anti-cancer activity, they had found it helpful against pre-eclampsia. In this dangerous complication of pregnancy, the mother develops hypertension and the fetus may fail to grow properly. The United States Preventive Services Task Force recommends that all women at high risk of this complication take a medication that can significantly reduce their likelihood of this worrisome condition ([Annals of Internal Medicine, Sept 9, 2014]).

The miracle medicine is low-dose aspirin. Women who took aspirin after the 12th week of pregnancy also lowered their risk of delivering their baby early or small for gestational age.

Doctors have been debating the pros and cons of aspirin for women at risk of pre-eclampsia for more than three decades. The new guidelines suggest that the controversy should now be considered closed, but pregnant women must check with their own health care providers to see whether this treatment is appropriate for them.

The Downsides of Aspirin:

No one should ever start taking aspirin on a regular basis without talking the benefits and risks of aspirin over with their doctor. Although aspirin can reduce the possibility of a second heart attack or stroke, it can also cause serious digestive tract irritation, including bleeding ulcers. There are also people who are allergic to aspirin and must avoid it for that reason.

One reader reported:

“I had internal bleeding from a prescribed aspirin regimen. I had no problems for five years taking 81 mg per day. When the bleeding started, I initially thought nothing was wrong. Finally, I could barely move and was taken to the emergency department. My hemoglobin was 7.1, while normal is 11 to 15. I spent a week in the ICU and received several blood transfusions for a bleed in my upper GI tract.”

Taking 100 to 250 mg vitamin C may help protect the digestive tract from aspirin-induced irritation (Alimentary Pharmacology & Therapeutics, May 2001; Journal of Physiology & Pharmacology, Nov. 2006, Suppl. 5). Anyone planning to take aspirin on a regular basis should discuss this with a physician.

What Dose of Aspirin?

Complications are more likely at higher doses. One reader wondered about the dose her husband was taking:

Q. My 70-year-old husband is taking two full-size aspirins a day to prevent heart problems. There are no heart problems in his family. He doesn’t believe me when I tell him this is too much. Your take?

A. Long-term aspirin use is NOT a do-it-yourself project. Despite the many benefits of aspirin, this drug can cause life-threatening bleeding ulcers. In older people, this can sometimes occur without warning symptoms.

This is a big dose and your husband must discuss it with his doctor. Research in high-risk individuals (people who have a stent) found that high-dose aspirin (more than 200 mg a day, which is less than one full-size 325 mg aspirin tablet) was associated with more complications but did not offer more benefit than low-dose aspirin at less than 200 mg daily (JACC. Cardiovascular Interventions, Dec. 2012). A so-called “baby” aspirin is 81 mg, but we believe that long-term use of even low-dose aspirin calls for medical supervision.

Age-Related Macular Degeneration:

People who are susceptible to wet macular degeneration should avoid aspirin, as it can make this condition worse (JAMA Internal Medicine, Jan. 21, 2013). A met-analysis covering ten studies found a weak but statistically significant association between aspirin use and the risk of age-related macular degeneration (Li et al, Journal of Clinical Pharmacy and Therapeutics, April 2015). More recent research demonstrates, however, that anti-platelet drugs (such as aspirin) and anticoagulants did not have a negative impact on vision among people with wet (neovascular) macular degeneration (Buitendijk et al, American Journal of Ophthalmology, March 2018). Scientists in Australia are conducting a clinical trial to determine the exact benefits and risks of aspirin with respect to macular degeneration (Robman et al, Contemporary Clinical Trials Communications, June 2017).

Aspirin and Other Drugs:

Anyone who is taking other medications must check with both the prescriber and the pharmacist before starting to take aspirin daily. Ask whether any of your medicines are incompatible with aspirin, for some are. One reader was curious whether ibuprofen and aspirin would interact:

Q. Are there problems associated with taking daily low-dose aspirin for cardiac protection along with ibuprofen for pain relief? I’ve read that taking an NSAID like ibuprofen can negate the desired effects of the aspirin.

A. It is estimated that half of older adults take aspirin regularly, in large measure to protect their hearts (Clinical Medicine & Research, online, Feb. 26, 2014). One way this ancient medicine works is by keeping the sticky part of blood (platelets) from clumping and causing clots that could trigger a heart attack or stroke.

Taking a nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen or naproxen may undo this cardiovascular benefit. That’s because such drugs compete with aspirin and keep it from doing its anti-clotting job. Research suggests that taking the NSAID pain reliever at least two hours after aspirin and eight hours before the next dose might reduce the potential interaction (Thrombosis and Haemostasis, May, 2013).

The People’s Pharmacy Perspective:

Our perspective on the benefits and risks of aspirin is that this must be determined on an individual basis. Clearly, researchers are still making new discoveries about how aspirin works (Li et al, Cellular Physiology and Biochemistry, online March 2, 2018). Over the years, it has become clear that the people who benefit most from taking aspirin as a preventive are those at high risk. As a result, it may make sense for people with heart disease to take low-dose aspirin to prevent a heart attack. Healthy people might be more likely to experience harm from aspirin, even at low doses.

Similarly, people with cancer or at high risk of certain cancers may be able to prevent its occurrence or recurrence. On the other hand, people without risk factors might be more likely to have problems than to prevent an extremely unlikely cancer.

We suspect there will be many more studies to clarify when aspirin could be helpful and when it is more likely to be dangerous. To learn more about what is currently known, you may wish to read our free Guide to Key Aspirin Information or listen to our interview (Show 945) with Dr. Tieraona Low Dog about vitamins and aspirin.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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