New recommendations on taking aspirin are likely to stir up debate among doctors.
They suggest that some people who haven't already had a heart attack should take a daily low-dose aspirin to prevent heart attacks and stroke, as well as colon cancer.
The recommendations from the U.S. Preventive Services Task Force (USPSTF) are likely to be controversial because even low doses of aspirin can cause sometimes deadly internal bleeding — both in the stomach and intestines and in the brain. It's not easy to tell who's at risk and the bleeding often doesn't cause symptoms.
But they're also very specific and based on studies that show who can benefit from taking a daily low-dose aspirin.
"This is a new approach that makes a great deal of sense," said Eric Jacobs, an expert on the effects of aspirin at the American Cancer Society. "No major health organization has previously recommended the use of aspirin to prevent cancer."
The USPSTF, whose recommendations often are used as the basis for medical policy, says adults in their 50s who have a 10 percent or greater risk of heart disease over the next 10 years should take a low-dose aspirin daily to prevent heart disease and colon cancer.
"Persons who are not at increased risk for bleeding, have a life expectancy of at least 10 years, and are willing to take low-dose aspirin daily for at least 10 years are more likely to benefit," the task force says in its recommendations.
"The USPSTF found adequate evidence that aspirin use reduces the incidence of colorectal cancer in adults after 10 years of use."
It's a draft statement and is being put out there for people to comment on.
There's not enough evidence to say if people under 50 or over 70 who have not already had a heart attack or stroke should take aspirin, the group adds. The risks of gastrointestinal (GI) bleeding and hemorrhagic stroke are small in adults under 60 and small to moderate in those in their 60s, the task force found.
"Evidence shows that risk for GI bleeding, with and without aspirin use, increases with age," the group wrote. People who have pain in their stomach or upper abdomen, who have ulcers or are taking other blood thinners have a higher risk, as do people with uncontrolled high blood pressure.
As with any drug, patients and their doctors must balance the benefits and risks of aspirin. It's clear that aspirin reduces the risk of heart attacks and strokes, and that it lowers the risk of colon cancer. Aspirin is a non-steroidal anti-inflammatory drug (NSAID). It helps reduce the rate of blood clotting and can lower inflammation.
"The rate of serious bleeding in aspirin users is about two to three times greater in patients with a history of a GI ulcer," the task force adds. "Men have twice the risk for serious GI bleeding than women."
Several experts said the group tried to be as specific as possible.
"They've tried to cut through a lot of the other recommendations that are out there using the most recent evidence, carefully evaluating it, and have come to what is about as clear as you can get it — because there isn't a study for every possible scenario," said Dr. Allen Taylor, chief of cardiology at Georgetown University.
At the very least, it should get people talking, Taylor said. "So there's really two sides. Get the right people on aspirin, and get the wrong people off aspirin. And so the more the public is aware of who can benefit from aspirin, the better off we are. It can trigger conversations with their doctors," said Taylor.
"If you have heart disease, the answer is very clear. You should really be on something — aspirin or something like aspirin," said Taylor.
This is called secondary prevention. The USPSTF is now saying that some people should take low dose (81 mg) aspirin for what's called primary prevention, meaning to prevent a first heart attack or stroke.
They used a calculator from the American College of Cardiology and American Heart Association to figure out who's at a 10 percent risk or greater. It takes account of cholesterol levels, blood pressure and smoking, as well as age, race and gender.
The benefits of aspirin only outweigh the risks in people who have already had some sort of heart event like a heart attack or in those at 10 percent risk or greater, the USPSTF says.
The USPSTF points out that heart disease and colon cancer kill many Americans.
"Cardiovascular disease, including heart attack and stroke, is responsible for 30 percent of all deaths in the United States," the task force says.
"More than 26 million adults have been diagnosed and are living with heart disease. Nearly 8 million adults have a history of heart attack and 6 million have a history of stroke. Colorectal cancer is the third most common cancer in the United States. In 2014, there were an estimated 137,000 new cases and 50,000 deaths due to colorectal cancer."
About 40 percent of American adults over 50 currently take a daily aspirin to prevent heart attacks or strokes, the USPSTF says.
Several experts welcomed the updated recommendations.
"While it is true that there are potential harms to long-term use of aspirin (namely bleeding), it is a very simple and cheap intervention that is already widely available and known to be relatively safe," said Dr. Ranit Mishori, a family physician at Georgetown University.
"While I am excited to offer this as an option to my patients, I will continue to emphasize and insist they adhere to other colorectal cancer prevention strategies such as maintaining a healthy diet—eating a diet rich in fruits and vegetables and low in red meat—exercising, not smoking, and to recommended colorectal screening protocols."
Mishori and Jacobs both said there's some evidence to suggest aspirin might protect against other cancers.
"There is more evidence about aspirin and colorectal cancer than there is about any other cancer. However, there is also good evidence that aspirin use also lowers risk of developing esophageal cancer, though this cancer is less common than colorectal cancer in the United States, and fairly good evidence for lowered risk of stomach cancer as well," Jacobs said.
"There is some evidence that aspirin might slightly lower risk of certain other cancers, including common cancers such as breast cancer, prostate cancer, and lung cancer, but this is evidence is too weak to make strong conclusions."