“It is critical that users are aware of the potential privacy risks,” Ikram said. “It is important to weigh the advantages and risks of using an app and decide accordingly whether it is worth sharing a piece of information that might be sensitive with the app or not. Similarly, it is rather important to be careful when granting these apps permissions to access specific categories of data on your mobile. For instance, these apps might not always need to access your list of contacts or your geolocation. Finally, clinicians recommending mobile apps related to their specialization area need to be aware of their potential risks and inform their patients.”

The new analysis is “impressive in the scale of what they’ve done,” said Dr. Seth Martin, an associate professor of medicine at the Johns Hopkins School of Medicine in Baltimore, director of the digital health innovation laboratory at the Ciccarone Center for the Prevention of Cardiovascular Disease, and co-director of the Center for Mobile Technologies to Achieve Equity in Cardiovascular Health at the Johns Hopkins Hospital.

“A key takeaway from this study is that you should be very careful of what you put on your phone and once you do put something on your phone, you should be mindful of the permissions you give,” Dr. Martin said, adding that privacy concerns aren’t the only issues.

“Does the app measure what it claims it measures,” said Dr. Martin, who was not involved in the new research. “What is the validation for those measurements. There have been issues with apps that claim to measure blood pressure. They actually do not do that.”

Another important question: “does the app help you take the actions you need to take to improve your health,” Dr. Martin said.