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 But by 2004, Merck had withdrawn the drug because studies showed it significantly raised the risk of heart attack.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.