“Lowering Your Blood Pressure Could Stave Off Dementia,” heralded the headline from Bloomberg, which was not alone in delivering the “good” news.
Time advised, “There May Finally Be Something You Can Do to Lower Your Risk of Dementia.”
Reuters’ headline was even more definitive. “Lowering Blood Pressure Cuts Risk of Memory Decline: US Study.”
Readers can be forgiven if they rushed to their doctors to discuss more aggressive blood pressure treatment. Who wouldn’t want to escape the scourge of dementia? But alas, most of the news stories beneath the headlines were as misleading as the headlines themselves.
This column is not intended to give advice on lowering blood pressure. Only doctors do that. Instead its goal is to tell readers that media stories sometimes misrepresent the results from scientific papers presented at medical meetings and how that can sometimes mislead the public. It’s also intended to help readers become more skeptical and cautious when they hear glowing reports about new medical treatments.
In discussing this study, the media mixed up mild cognitive impairment with dementia. According to the press release from the Alzheimer’s Association International Conference where the study was recently presented, mild cognitive impairment (MCI) causes a slight but noticeable and measurable decline in cognitive abilities including memory and thinking skills, but the decline is not severe enough to interfere with daily life. People with this kind of impairment may have an elevated risk for developing Alzheimer’s disease and other dementia later on, but they won’t necessarily develop those diseases.
In other words, mild cognitive impairment and Alzheimer’s disease are two different animals, but the news reports didn’t make that clear.
Dr. Michael Joyce is a writer-producer with Health News Review.org, the site that examines medical studies and tries to keep the media honest. He said “not a single major news outlet we came across noticed that the study did not achieve what’s called in scientific circles its “primary end point.” That is, news reports failed to explain that the study did not prove that tightly controlling blood pressure prevented dementia, which was the main result researchers were looking for.
Furthermore, Joyce said of the stories Health News Review examined, only one, from the Wall Street Journal, correctly reported that the absolute reduction in risk of getting dementia was just over one percentage point when blood pressure was tightly controlled so that the first number – or systolic pressure – in blood pressure measurement is equal to or less than 120. Simply put, the absolute risk reduction is the difference in the rate of contracting the disease between the group that got the treatment and a comparison group that didn’t.
Instead of reporting the absolute risk reduction, most media reported something called the relative risk, which measures the probability of an event occurring in one group compared to the probability of the event occurring in the comparison group. News outlets reported that of the 9,000 adults with increased cardiovascular risk (but no known diabetes, dementia, or stroke), those who were being aggressively treated for high blood pressure were 19 percent less likely to develop mild cognitive impairment than those being treated less intensely.
Which sounds better: 1 percentage point or 19 percent? So you see why news outlets like to trumpet the relative risk reduction. It’s usually a larger number and grabs readers’ attention. But it can give the wrong impression. “Intentionally highlighting the more dramatic relative numbers, rather than the more accurate absolute numbers, can badly mislead readers,” Joyce said.
This story had yet another problem. Media made almost no mention of the potential harms from aggressively lowering blood pressure. They are not insignificant. Dr. Preeti Malani, a professor of medicine at the University of Michigan, says the decisions regarding a blood pressure goal are very nuanced and individualized. She said that although data from this study “may be encouraging, I’d like to see something more definitive before calling this an effective means to ‘stave off dementia.’ That’s overstated based on this abstract.”
Next time you see a story about a medical study, consider these tips from Health News Review for evaluating what you see and hear.
* See if the absolute risk reduction is reported. That’s the number that counts. Pay little attention to the relative risk reduction, which may be a bigger number.
* Are potential harms from a new treatment adequately explored? There’s almost always a tradeoff between harms and benefits of any new treatment.
* See if someone other than the study author is quoted. Independent sources should be used to confirm or refute the findings.
* Beware of news reports based on research presented at medical meetings. “Very, very rarely do such meeting abstracts contain breakthroughs, paradigm shifts or unassailable information that will immediately change patient care,” Joyce said.
What has been your experience with over-hyped medical studies? Write to Trudy at firstname.lastname@example.org.