Smartwatch accuracy issues identified in sleep and calorie tracking studies

Recent scientific studies have highlighted significant inaccuracies in the health metrics provided by consumer smartwatches, specifically regarding sleep quality and calorie expenditure.

Researchers from Duke University and the Mayo Clinic evaluated five studies involving 2,000 participants. They found that wearable devices, including Fitbit and Apple Watch, only explained between 2.5% and 16.2% of the difference in subjective sleep quality. While devices can track duration and regularity in healthy individuals, accuracy drops significantly for those with sleep disorders or mental health challenges, as sensors cannot capture all factors affecting rest.

Separately, a study from Florida International University found that smartwatches systematically overestimate calories burned during exercise. Testing devices such as Apple Watch, Garmin, Samsung Galaxy Watch, and Fitbit, researchers noted a median error margin of 15% to 25%. The inaccuracy increases with a user's body fat percentage, with some overestimations exceeding 100%. This discrepancy is particularly problematic for individuals using the data to manage weight loss through caloric deficits.