Advice on daily aspirin keeps changing

Daily low-dose aspirin, once seen as a fairly innocuous way to cut the risk of heart attack or stroke, continues to lose its luster for people 40 and up who have not had one of these events.

“In the past, we used to think: ‘Aspirin, no harm, why not take it?’” said Cardiologist John J. Guerin, MD, who practices at Cape Cod Healthcare’s Cardiology Centers in Falmouth and Sandwich.

Analysis of research into the effects of a low-dose (less than 100 mg, typical low dose is 81 mg) aspirin regimen on different age groups has caused the U.S. Preventive Services Task Force to update its 2016 recommendations. The task force, which is not a federal government body but an independent panel of volunteer experts, weighed the beneficial effects versus the negative.

According to the task force, aspirin inhibits platelet function, thereby reducing the formation of clots and atherosclerosis (plaque buildup on arterial walls). This helps prevent heart attacks and ischemic strokes, the most common type, which are caused by clots. On the negative side, aspirin also blocks production of prostaglandins that protect the lining of your digestive tract, raising the risk of gastrointestinal bleeding. Aspirin’s blood-thinning properties can increase the chance of bleeding inside the skull and hemorrhagic stroke, when blood leaks into the brain.

Findings and new recommendations

Findings:

• A low-dose aspirin regimen is of little net benefit for men and women 40-59 years old who have 10 percent or more chance of cardiovascular disease event and have not had a stroke or heart attack.
• A low-dose aspirin regimen has no net benefit to prevent heart attack or stroke in people 60 and older who have not had a stroke or heart attack.

The task force recommends:

• People in the 40-59 age group discuss with their doctor whether to begin a low-dose aspirin regimen, with the decision being made on an individual basis. More benefit is likely for people at higher risk. This guidance does not apply to people on blood-thinning medications or with certain conditions, such as digestive tract ulcers or bleeding. This advice changes from the task force’s 2016 recommendation of a low-dose aspirin regimen for men and women 50-59 with a 10 percent or more chance of cardiovascular disease risk over the next 10 years.
• People 60 and older should not start a low-dose aspirin regimen, if they have not had a stroke or heart attack. The risk of stroke and bleeding increases with age, Dr. Guerin said. The task force previously recommended that the decision to start such a regimen for people 60-69 should be done on an individual basis.

Dr. Guerin noted that these recommendations are for “primary prevention” – for people who have not had a heart attack or stroke. They don’t apply to people who have experienced one of these events. For most people in that group, aspirin can be an important part of “secondary prevention,” he said, citing the “overwhelming benefit of aspirin therapy for those folks.”

The changing recommendations from the task force and other medical organizations may be confusing, but medical advice evolves as newer research improves understanding, Dr. Guerin said.

“It does make sense,” he said. “We have to balance the benefit and risk.”

According to the American College of Cardiology (ACC), the task force’s new advice “generally aligns” with the primary prevention guidelines the ACC and American Heart Association jointly put forth in 2019. Those guidelines say low-dose aspirin may be considered in people 40-70 years old at elevated risk of atherosclerotic cardiovascular disease, but not for people over 70 and anyone at high risk of bleeding. Another medical body, the American Academy of Family Physicians backed the task force’s 2016 recommendations and in early May indicated it would take a formal position on the new guidelines after reviewing the evidence summary and modeling study used.

Among the factors considered in calculating a patient’s risk of a cardiovascular event are whether they have diabetes, high blood pressure, or high blood levels of low-density cholesterol, if they smoke, and their age and family health history, Dr. Guerin said. He urged people to talk with their doctor before starting to take aspirin on a regular basis. Aspirin may not be indicated for people with gastric ulcers or certain other conditions or who take blood-thinners.

“I told two or three people this week to stop (taking low-dose aspirin daily).” Dr. Guerin said.

The task force reviewed evidence from 13 clinical trials with more than 161,000 participants before making its new recommendations, which were issued April 26, 2022. It did find that use of low-dose aspirin as a primary preventive lowered the risk of non-fatal heart attacks and ischemic (clot-caused) strokes. However, a similar significant decrease of fatal cardiovascular events or death from any cause was not found.

Low-dose Aspirin and Colorectal Cancer

The task force also concluded there’s not enough evidence to recommend that low-dose aspirin reduces the incidence of, or deaths from, colorectal cancer and urged more research be done. Few studies were found to review, and the results of these were mixed. One study reported increased risk of death from colorectal cancer associated with aspirin use in older people. Four studies found no association between aspirin use and incidence of colorectal cancer over a 10-year period. Two trials reported aspirin was associated with lower risk of death, but only one said the trend was statistically significant.