Why Does Medical Advice Often Change? Doctors Explain
Medical reversals about menopause hormones, knee surgery and vitamins over the years have left patients confused. But doctors say these pivots often are good medicine.,
Is the New Aspirin Advice a Medical Flip-Flop, or Just Science?
Medical reversals about menopause hormones, knee surgery and vitamins over the years have left patients confused. But doctors say these pivots often are good medicine.
When it comes to preventive health, few tenets are as entrenched as daily aspirin. For more than 30 years, many people have relied on the pain reliever for added protection against a first heart attack or stroke.
So it came as a shock to many this month when an influential expert panel, the U.S. Preventive Services Task Force, seemed to reverse decades of medical practice, announcing that daily low-dose aspirin should no longer be automatically recommended in middle age to prevent heart attack.
“It was almost like a vitamin to some people,” said Dr. Eric Topol, a cardiologist and professor of molecular medicine at Scripps Research in La Jolla, Calif.
At a time when many people already feel whipsawed by shifting pandemic advice (on masks, viral transmission and booster shots), the new aspirin recommendations left some shaking their heads.
“Wait long enough, and smoking and heavy cream will be good for you,” Richard Koss, an economist in New York, wrote in a comment after reading about the new guidelines. “The vast majority of people are fed up with this sort of thing and, rightly, pay it no attention.”
But experts say it should be reassuring to patients to know that even the most trusted medical guidelines are being reviewed and updated as scientific understanding evolves.
“It seems like it happens overnight, but this is how science works,” Dr. Sophie M. Balzora, a gastroenterologist at N.Y.U. Langone Health, said. “If we had the same guidelines all the time, then the question would be: Are we really advancing science? Are we really learning more?”
A history of medical flip-flops
Shifting medical advice is surprisingly common, and it tends to fall into three categories: emerging guidance, replacement advice and reversals.
Emerging guidance comes during times of crisis — like pandemics — and is destined to change quickly. In the past several months, guidance about the best way to treat Covid patients, masks to prevent transmission and the limits of vaccine protection have all shifted as knowledge of the coronavirus and its variants has evolved.
Sometimes it’s hard to tell the difference between replacement advice, which is issued when research improves on advice that came before it, and a full reversal, which comes about because a common medical practice got ahead of the science and never actually worked or even caused harm. Here are some examples of true medical flip-flops in recent years.
Menopause hormones to protect the heart: In 2002, decades of advice about the heart benefits of menopause hormones seemed to change overnight when a major study called the Women’s Health Initiative was halted after researchers detected more heart attacks in the women taking hormones. In hindsight, doctors had misinterpreted data from observational research. The current advice: Hormones can relieve menopause symptoms but shouldn’t be used for chronic disease prevention.
Vioxx as a lower-risk arthritis treatment: In 1999, the Food and Drug Administration approved Vioxx as a breakthrough pain reliever because it lowered the risk of gastrointestinal problems. But by 2004, Merck had withdrawn the drug because studies showed it significantly raised the risk of heart attack.
Arthroscopic surgery on aging knees: For years, the partial removal of torn meniscus tissue was the most common orthopedic procedure in the United States, with about 700,000 performed a year. In 2013, a researcher in Finland compared the operation to a “sham” procedure and found there was no benefit. Most doctors now recommend physical therapy instead.
Vitamin megadoses to lower cancer and heart risk: For years, doctors believed various vitamins could lower risk for cancer and heart disease, but a number of studies showed just the opposite. A study of beta carotene and vitamin A found that the supplements actually increased the risk of lung cancer in male smokers. A study of vitamin E and selenium, thought to protect against prostate cancer, increased risk for the disease.
Stents for stable heart disease: Doctors used to insert stents — tiny wire mesh tubes that prop open arteries — in millions of otherwise stable patients with heart disease. A study found that the surgical procedure was no better than drug therapy for preventing heart attacks.
Dr. Vinay Prasad, associate professor at the University of California San Francisco, and Dr. Adam S. Cifu, a professor of medicine at the University of Chicago Department of Medicine, coined the term “medical reversal” and concluded that about 40 percent of common medical practices that they reviewed turned out to be useless or harmful. In their book, “Ending Medical Reversal: Improving Outcomes, Saving Lives,” they noted that most of these failed treatments were initially embraced because they were based on logical reasoning.
“The thing that’s often behind reversal: All of these things have a good story, they have good pathophysiological rationale,” Dr. Cifu said. “They should work. But things only work if they’ve been shown in people to work, and people are so complicated.”
The reason aspirin advice changed
While daily aspirin can lower risk of heart attack or stroke, it can also increase risk for internal bleeding. Although the absolute risk of a bleeding event is relatively low, the risk increases with age.
Several experts say the new guidance from the Preventive Services Task Force to curb aspirin use is not a true medical reversal and should be viewed as updated advice replacing outdated guidance, which is why the panel exists in the first place. Earlier this year, the task force lowered the age of regular colonoscopy screening to 45, down from 50. The panel caused an uproar several years ago when it recommended that women start breast cancer screening at age 50, instead of 40.
“The task force is just constantly re-evaluating based on what data were available,” Dr. Barron H. Lerner, a medical historian and professor of medicine at N.Y.U. Langone, said. “This might be seen as flip-flopping, but it is really making adjustments based on the evolving science.”
For people who have had a heart attack, stroke or other major cardiovascular issue, the case for using aspirin to protect them from a second event remains strong. The new Preventive Services Task Force guidelines don’t change that advice.
What has changed is the guidance for using aspirin to prevent a first heart attack or stroke.
The early evidence in support of aspirin to protect the heart came in 1988 from a randomized controlled clinical trial of 22,071 male physicians, some of whom took regular doses of aspirin. The study was stopped early because the benefit in the aspirin group was so drastic — cutting heart attack risk by nearly half.
As a result of the physician study and other research, the task force began updating its aspirin advice. In 2002, the panel was cautious, urging patients to talk to their doctors. But by 2016, the task force had recommended low-dose aspirin for adults 50 to 59 at risk of heart problems.
But in the years since the early research showed such a striking benefit to aspirin use, much about the population has changed. Fewer people smoke, and doctors have better treatments to control diabetes, high blood pressure and cholesterol, issues that all affect risk for heart attack and stroke. Aspirin still works to protect the heart, but doctors say the benefits aren’t as pronounced now that other more effective treatments have emerged. As a result, the risks of aspirin, including gastrointestinal bleeding and brain hemorrhage, are of greater concern, though they remain low.
Three major studies of aspirin influenced the task force advice this year.
A 2018 study of more than 19,000 healthy people 65 and older showed that regular low-dose aspirin use significantly raised bleeding risk and didn’t significantly lower risk of heart problems compared with a placebo.
A 2018 study of aspirin use in 15,480 people with diabetes found a benefit to the heart but also a significant bleeding risk.
A seven-country study of aspirin use in 12,546 moderate-risk people in their 50s and 60s was inconclusive, most likely because other prevention strategies were muting the effect of aspirin.
As a result, the task force this month said that people 60 and older should definitely not start taking aspirin to prevent a first heart attack or stroke. For people ages 40 to 59, the task force suggested discussing the risks and benefits with a doctor.
“There is new evidence, and it’s about how we put all the evidence together and apply it to people today. How do we apply it to the U.S. population in 2021?” said Dr. Chien-Wen Tseng, a member of the task force and research director at the University of Hawaii John A. Burns School of Medicine.
Dr. Cifu said the revised aspirin guidelines were a sign that the task force review process was working and should give people more confidence in the advice.
“Things that we knew were right in the late ’80s early ’90s need to be rechecked to see if they’re still right, given that we’re all quite different than 30 years ago,” Dr. Cifu said. “It’s a little uncomfortable that things don’t stay the same forever, but it’s good that medicine is checking itself.”
Dr. Tseng said she hoped the new guidance about aspirin would prompt more people to talk to their doctors about their heart health.
“One of the key messages we need to get out is that aspirin isn’t like a vitamin,” Dr. Tseng said. “There are potential benefits and potential risks. Everybody should be having a conversation with their clinician instead of just opening a bottle and taking aspirin automatically because they’ve reached a certain age.”