(Reuters Health) - - For years, researchers have been studying medical conditions using huge swaths of patient data with identifying information removed to protect people's privacy. But a new study suggests hackers may be able to match "de-identified" health information to patient identities.

In a test case described in JAMA Network Open, researchers used artificial intelligence to link health data with a medical record number. While the data in the test case was fairly innocuous - just the output of movement trackers like Fitbit - it suggests that de-identified data may not be so anonymous after all.