Activity trackers may overestimate sleep time

New York

"Wearable devices that track physical activity, sleep and other behaviours are growing significantly in popularity," said study co-author Robert Furberg from RTI International, a nonprofit organisation based in North Carolina, US.

The researchers conducted a systematic review of 22 published articles researching the ability of Fitbit and Jawbone -- two popular activity trackers -- to measure steps, distance, physical activity, calories and sleep.

Several studies indicated that the step counting feature was accurate both in the lab and in the field. Only one study assessed distance tracking for the Fitbit, finding that the device tends to over-estimate at slower speeds and under-estimate at faster speeds.

Two field-based studies compared accelerometry-assessed physical activity to results from the trackers, with one study finding high correlation while another study noted a wide range in correlation.