July 3, 2019

Editor's note: This popular story from the Daily Briefing's archives was republished on June 4, 2020.

A recent meta-analysis in the journal eLife identified nearly 400 routine practices that have been debunked by studies in leading medical journals. Writing for the New York Times, Gina Kolata rounds up 10 "of the most notable findings."

Cheat sheets: Meta-analyses—and 5 other components of evidence-based medicine

Details on the meta-analysis

For the analysis, researchers looked at more than 3,000 studies published between 2003 and 2017 in JAMA and The Lancet or between 2011 and 2017 in the New England Journal of Medicine. The researchers particularly examined a subset of findings known as "medical reversals"—that is, findings that contradict an existing medical practice by demonstrating via randomized controlled trials that the practice is "no better than a prior or lesser standard of care."

Busting 10 'medical myths'

In looking through the studies, the researchers identified 396 medical reversals. Here are 10 of their most notable findings, according to Kolata.  

  1. Exposing children to peanuts before age three will not increase their risk of peanut allergies: While pediatricians tell parents to avoid exposing children to peanuts before age three, research shows that exposure to peanuts even before one year of age does not correlate with higher risk of peanut allergy.

  2. Consuming fish oil won't cut your heart disease risk: Eating a diet higher in fatty fish has been tied to a lower incidence of heart disease, a finding that spurred people to start eating supplements that contained omega-3 fatty acids—which are found in fish. However, a trial of 12,500 people at risk for heart disease found that eating the supplements didn't reduce heart attack risk.

  3. Giving teenage girls dolls will not reduce their risk of becoming pregnant: Some schools give teenage girls lifelike dolls that require care similar to what a real infant needs, like changing diapers and cuddling. The idea was this would inform young women about the difficulty of becoming a parent at that age. However, not only does the intervention not work, research shows a slightly higher likelihood of pregnancy among teens who got the dolls than among teens who didn't.

  4. Ginkgo biloba won't prevent memory loss or dementia: While the supplement is promoted as a way to preserve memory, a large federal study from over a decade ago showed the supplements did not confer these benefits. Nonetheless, ginkgo is still a $249 million industry, according to Kolata.

  5. Opioids are not better than less addictive painkillers for acute ED pain: While opioids are "powerful drugs," Kolata writes, a study found less addictive painkillers are just as effective at relieving pain for ED patients.

  6. Treatment with testosterone won't help men with memory loss: While early studies suggested that middle-aged men with higher testosterone appeared to have better preserved tissue in certain parts of the brain, a clinical trial found that administering testosterone didn't work any better than a sugar pill at staving off memory loss in older men.

  7. Keeping your house free of common pests won't affect the odds of an asthma attack: Leading medical groups have advised keeping your house free of dust mites, cockroaches, and mice if someone in your family has asthma. The idea was that allergic reactions could prompt asthma attacks. However, managing pests intensively in homes with children who were sensitized to mouse allergens did not reduce the frequency of an attack, a 2017 study found.

  8. Step counters and calorie trackers won't help with weight loss: While dieters have been advised to track steps and calories, a study found that followed people for two years found people who wore devices to track steps and calories actually lost less weight than people who didn't.

  9. Try physical therapy before surgery for a torn meniscus: A torn meniscus is a painful tear in the cartilage of the knee, frequently caused by osteoarthritis, and it's often treated surgically to prevent pain from lingering, Kolata writes. However, research shows that when patients with moderate arthritis who had a torn meniscus were randomized to receive surgery or physical therapy, both groups showed the same extent of improvement.

  10. A baby does not have to be delivered immediately after a woman's water breaks prematurely: When a woman delivers a few weeks ahead of her due date, obstetricians typically have induced labor out of concern that that bacteria would intrude the sterile environment around the fetus and cause infection. However, a clinical trial found the fetus is not at greater risk for infection in these cases, so long as doctors monitor the fetus closely. Further, newborns who gestate longer are healthier, have less respiratory distress, and have lower risk of death than those delivered prematurely right after the mother's water breaks (Kolata, New York Times, 7/1; Herrera-Perez et al., eLife, 6/11).

Cheat sheets: Evidence-based medicine 101

Been a while since your last statistics class? It can be difficult to judge the quality of studies, the significance of data, or the importance of new findings when you don't know the basics.

Download our cheat sheets to get a quick, one-page refresher on some of the foundational components of evidence-based medicine.

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