Health trackers worn on the wrist could pick up Covid-19 days before symptoms even appear, research suggests.
The trackers monitor changes in skin temperature, heart and breathing rates and could be combined with artificial intelligence (AI) to offer a diagnosis, according to a new study.
A team writing in the journal BMJ Open tested the AVA bracelet, a fertility tracker that people can buy online to track the best time to conceive.
It monitors breathing rate, heart rate, heart rate variability, wrist skin temperature and blood flow.
In the study, 1,163 people under the age of 51 in Lichtenstein were followed from the start of the pandemic.
They were asked to wear the AVA bracelet at night, with the device saving data every 10 seconds. People have to sleep for at least four hours for it to work.
The bracelets were synchronised with a smartphone app, with people recording any activities that could affect the results, such as alcohol, prescription medications and recreational drugs.
They also recorded possible Covid-19 symptoms such as fever.
All those in the study took regular rapid antibody tests for Covid while those with symptoms also took a PCR swab test.
Overall, 1.5 million hours of physiological data were recorded and Covid was confirmed in 127 people, of which 66 (52%) had worn their device for at least 29 consecutive days and were included in the analysis.
The study found there were significant changes in the body during the incubation period for the infection, the period before symptoms appeared, when symptoms appeared and during recovery, compared to non-infection.
Overall, the tracker and computer algorithm identified 68% of Covid-19 positive people two days before their symptoms appeared.
The team, including from the Cardiovascular Research Institute of Basel, concluded there were limits to the research, including that not all Covid cases were captured.
But they added: “Wearable sensor technology can enable Covid-19 detection during the pre-symptomatic period.
“Wearable sensor technology is an easy-to-use, low-cost method for enabling individuals to track their health and wellbeing during a pandemic.
“Our research shows how these devices, partnered with artificial intelligence, can push the boundaries of personalised medicine and detect illnesses prior to (symptom occurrence), potentially reducing virus transmission in communities.”
The algorithm is now being tested in a much larger group (20,000) of people in the Netherlands, with results expected later this year.