In one study, researchers who did a sweep of YouTube videos on high blood pressure found that one-third offered "misleading" information. Most often, that meant the video advocated supplements or other alternative therapies that haven't been scientifically proven to lower blood pressure.
"It's quite concerning," said lead researcher Dr. Nilay Kumar, who is scheduled to present the findings Monday at the annual meeting of the American Society of Hypertension in New York City.
"The videos that were misleading seemed to get a lot more hits than the videos from authoritative sources," said Kumar, a physician with the Cambridge Health Alliance in Massachusetts.
Those authoritative sources included the American Heart Association, medical universities and professional medical societies, Kumar said.
The other study, scheduled for presentation at the same meeting, looked at the accuracy of two home blood pressure devices that people connect to their iPhones. In each case, an app keeps track of their numbers and can send the information to their doctor.
Overall, the study found, both devices were inaccurate when compared with traditional doctor's-office measurements. Across 112 readings taken by the same person, one device gave numbers that were too high -- by an average of 3 to 5 points -- while the other gave numbers that were 5 points too low.
The bottom line? The study "sends a loud and clear message that such technology needs to be vetted against the standard technology before accepting these blood pressure readings at face value," said Dr. Domenic Sica, president-elect of the American Society of Hypertension.
"This technology clearly needs better refinement," said Sica, who was not involved in either new study.
According to the U.S. Centers for Disease Control and Prevention, almost one-third of U.S. adults have high blood pressure. But only about half of them have the condition under control.
Elevated blood pressure increases your risk for heart disease and stroke, the leading causes of death in the United States.
It's important that people with high blood pressure be "self-empowered" to take part in their own care, Sica said. But they also have to be careful about their sources of information.
Since so many people get health information online, Kumar's team wanted to check the accuracy of blood pressure information on YouTube -- a site that draws more than 1 billion "unique users" each month, according to the company.
The researchers searched the site using the terms "high blood pressure" and "hypertension," and ended up screening 176 videos -- a small sampling of the total hits their search retrieved.
Overall, the majority of the videos were deemed "useful." They included information on how high blood pressure develops and how to prevent and treat it. But one-third provided misleading information, Kumar's team found.
Often, those videos focused on supplements or other therapies that aren't proven to lower blood pressure -- such as L-arginine, garlic and coenzyme Q10 supplements, according to Kumar.
Many also featured ads for the products, which "suggests they were driven by financial motivations," Kumar said.
If you go online for blood pressure information, he suggested you stick with reliable sources such as the American Heart Association or the U.S. National Library of Medicine website Medline Plus.
Sica agreed. As for iPhone blood pressure devices, he said questions remain. It's not clear, for example, how they stack up against traditional home blood pressure monitors, he noted.
But those traditional devices are not all the same, either. In general, the heart association and other groups advise people to use automated (rather than manual) monitors that have an arm cuff. Devices that take wrist or finger measurements are less reliable.
Data and conclusions presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.
The American Heart Association has advice on how to monitor your blood pressure.