7/24/16: TO TAKE OR NOT TO TAKE: Aspirin in the Primary Prevention of Cardiovascular Disease & Cancer

aspirin

 

If you have never had a heart attack or a stroke and have no known cardiovascular disease (CVD), should you take aspirin daily to protect you from a future, possibly catastrophic cardiovascular event?

What about cancer prevention? Will a daily dose of aspirin protect you from developing any cancers?

It is well known that people who have had a myocardial infarction (the medical term for an “attack” caused by an obstruction of coronary blood flow) or an ischemic stroke (an obstruction in cerebral blood flow) can significantly reduce their risk of having another and of dying from CVD by taking daily, low-dose aspirin. A daily “baby aspirin” of 75 to 100 milligrams—81 mg. is an oft-recommended dose—will suffice.

Clinical evidence also exists to suggest that aspirin might protect against certain cancers, particularly colorectal cancer (CRC), which is cancer of the colon and/or rectum. Aspirin reduces inflammation, which, some published reports suggest, seems to promote cancer. (See MD Anderson Cancer Center, “Can a Daily Aspirin Lower Your Cancer Risk?” at https://www.mdanderson.org/publications/focused-on-health/november-2014/low-dose-aspirin-cancer-prevention.html.)

The U.S. Preventive Services Task Force (USPSTF) recently revisited its 2009 recommendations for the use of aspirin in the prevention of CVD and CRC and substantially altered its assessments. It no longer touts aspirin use for everyone over age 50, reflecting far less certainty about its benefits for older healthy adults.

(The USPSTF’s decision analysis about aspirin use and the new clinical evidence it considered are detailed in the June 21, 2016 issue of Annals of Internal Medicine. See http://annals.org/issue.aspx?journalid=90&issueid=935365&direction=P, for the issue’s table of contents, and http://annals.org/article.aspx?articleID=2513176 for a key article.)

The use of aspirin in the prevention of complications or recurrence of an established condition is known as secondary  prevention. According to the USPSTF, the evidence of aspirin’s net benefit in secondary prevention remains strong and clear.

Primary  prevention describes the use of aspirin or another medical treatment to prevent diseases or their complications before they occur. As you would imagine, endorsing primary-preventive treatment in healthy individuals, who differ from each other, is much trickier that endorsing secondary prevention, especially when the treatment, to be effective, must be long-term.

Aspirin, like all drugs, poses the risk of adverse effects. The most serious among them is internal bleeding, typically in the gastrointestinal tract (stomach, small intestines). But aspirin, which is an analgesic and anti-inflammatory drug and has an anti-coagulant effect (by inhibiting platelet clumping), can induce bleeding elsewhere in the body, including in the brain. Because uncertainty exists in the benefits-versus-harms relationship of long-term  aspirin use, according to the USPSTF, physicians face a clinical dilemma in deciding whether to recommend that a patient take aspirin for primary prevention of CVD and CRC. You, the patient, share that dilemma.

Question: To take or not to take?

**

The USPSTF is an independent panel of primary-care physicians and epidemiologists who are appointed, funded, and supported by the U.S. Dept. of Health and Human Services’ Agency for Healthcare Research and Quality. It makes recommendations about the effectiveness of specific preventive care services for patients without regard to their cost.

The task force does not speak for the government or for the medical profession. It looks at the clinical science and reaches conclusions based on the evidence. But keep in mind that the USPSTF is only one authoritative source; it is neither right nor wrong.

The USPSTF’s 2009 recommendations for primary-prevention aspirin use distinguished between men and women categorically and advised men as young as 45 to initiate aspirin dosing. In a substantial departure, the USPSTF’s 2016 recommendations do not advise anyone under 50 to take aspirin for prevention and differentiate individuals by their “10-year CVD risk,” not by sex, although sex is incorporated into the 10-year risk calculation.

I addressed 10-year CVD risk, a calculation devised by the American College of Cardiology/American Heart Assn. in 2013, in an April 30, 2016 “tidbit” on this website, in which I reported that cardiologist Dr. David Pearle of the Georgetown medical faculty always computes a patient’s 10-year risk during an initial visit. See https://annsjoerdsma.com/tidbits/.

You can calculate your own 10-year CVD risk at http://cvdrisk.nhlbi.nih.gov/, a site maintained by the National Heart, Lung, and Blood Institute of the NIH.

Primary risk factors for CVD include older age, male sex, race/ethnicity, abnormal lipid levels, high blood pressure, smoking, and diabetes. The 10-year risk calculation takes into account your sex, age, total and HDL cholesterol values, systolic blood pressure (the upper number of a BP reading, when the heart is contracting), and smoking habits.

The USPSTF now advises adults aged 50 to 59 who have a 10 percent or greater 10-year CVD risk and can expect to live at least another 10 years, and who are not at increased risk for bleeding, to start taking a low-dose aspirin daily and continue for at least 10 years to prevent CVD and colorectal cancer.

Among the people who have an increased risk of suffering a GI bleed while on aspirin are those who have peptic ulcers or who take 1) an anticoagulant, such as warfarin (Coumadin®), 2) corticosteroids, or 3) a non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen (e.g., Advil®) and naproxen sodium (e.g., Aleve®). All of these drugs also pose a risk of bleeding. Aspirin is an NSAID that treats inflammation and pain and reduces the chance that blood clots will form inside any diseased arteries. (I covered atherosclerosis, the accumulation of plaque on the walls of arteries, in a Facebook post last week: http://www.facebook.com/annsjoerdsmaauthor/.)

Interestingly, the USPSTF only assigns a grade of “B” to its updated recommendation for 50- to 59-year-old adults, which means it determined that there is a “high certainty that the net benefit [of aspirin use] is moderate or there is moderate certainty that the net benefit is moderate to substantial.” In contrast, an A grade reflects a “high certainty that the net benefit is substantial.”

The USPSTF further recommends that adults aged 60 to 69 who have a 10 percent or greater 10-year CVD risk and can expect to live at least another 10 years, and who are not at increased risk for bleeding, decide for themselves whether to initiate low-dose aspirin for the primary prevention of CVD and CRC. It gives this recommendation a “C,” leaving the treatment up to “professional judgment and patient preference.” The USPSTF is convinced only that there is “at least moderate certainty that the net benefit is small.”

The USPSTF gives no recommendations for adults younger than 50, or those 70 and older, who have no history of CVD or CRC, because the current evidence from clinical studies is insufficient to assess the “balance of benefits and harms of initiating aspirin use for the primary prevention of CVD and CRC.” Grade: I, for insufficient.

Just seven years ago, the USPSTF assigned A grades to recommendations that men aged 45-79 and women aged 55-79, whose risk of bleeding did not outweigh the potential benefits of primary prevention, take aspirin. Its revisions reflect a recognition of the uncertainty that has emerged with further clinical studies and analyses. Aspirin is not the panacea it once seemed.

**

I’m 61 and have never had a myocardial infarction or ischemic stroke or any symptoms of cardiovascular disease. My most recent blood-pressure reading was 108/62, which is normal for me. My most recent HDL was 74, and total cholesterol was 158. I exercise regularly, do not smoke, and maintain a healthy weight. But there is heart disease on my father’s side of my family, as well as colorectal cancer.

Should I be taking aspirin daily?

When I plugged in the numbers to compute my 10-year CVD risk, I came up with a score of 1 percent. One of 100 people who have my level of risk will have a myocardial infarction in the next 10 years. I am outside of the USPSTF’s defined risk group.

But what about colorectal cancer? According to the USPSTF, a patient must take aspirin for at least five to 10 years to realize a potential health benefit in colorectal-cancer prevention.

No, thank you. I take a lot of ibuprofen to treat flare-ups of chronic back pain—aspirin doesn’t touch this pain—and am much too concerned about bleeding to combine these NSAIDs. I’ll keep current with my colonoscopies and watch the USPSTF and medical journals for clinical updates on aspirin’s value in preventing cancer. There is much more yet to learn.

Ann, 7/24/16

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