Owners of devices such as Fitbits become more in tune with their health but suffer guilt and anxiety when they miss exercise targets or misinterpret data, dailymail.co.uk reported.

They may link a fast pulse with an increased risk of heart attack or fear that a lower than usual amount of sleep will exacerbate their illness.

Dr. Tariq Osman Andersen of the University of Copenhagen, who completed the study with help from health firm Vital Beats, said: “Our study shows that, overall, self-measurements are more problematic than beneficial when it comes to the patient experience.

“Patients begin to use the information from their Fitbits just as they would use a doctor. However, they don’t get help interpreting their watch data. This makes them unnecessarily anxious, or they may learn something that is far from reality.”

Published in the Journal of Medical Internet Research, the study examined 27 heart patients who used fitness watches to measure sleep, heart rate and physical activity.

Although the patients learned more about their illnesses and were motivated to exercise during the six months that they wore the watches, they also became more anxious.

Andersen said: “The problem is you cannot use data directly related to heart disease because the watch is designed for sports and wellness, as opposed to managing disease.’

The researchers said fitness watches and their accompanying apps offered great promise for heart patients but should be used in partnership with healthcare professionals to limit unwanted side effects.