Table 1.
Description and categorization of the feature set.
| Feature category | Feature description | Total COVID-19 individual tests | Number of individuals | Fitbit users [%] | Available days median [IQR] |
|---|---|---|---|---|---|
| Symptoms features | Fatigue | 1149 | 1091 | — | — |
| Headache | 1104 | 1061 | — | — | |
| Difficulty breathing | 208 | 206 | — | — | |
| Diarrhea or vomiting | 378 | 368 | — | — | |
| Decrease in taste smell | 247 | 247 | — | — | |
| Cough | 892 | 859 | — | — | |
| Fever chills or sweating | 660 | 645 | — | — | |
| Congestion Or runny nose | 1152 | 1097 | — | — | |
| Neck pain | 409 | 396 | — | — | |
| Body aches | 823 | 795 | — | — | |
| Sore throat | 973 | 922 | — | — | |
| Stomach ache | 312 | 302 | — | — | |
| Sensor features (activity) | Total number of daily steps | 9348 | 6983 | 82% | 673 [507–707] |
| Total daily distance traveled on foot | 9281 | 6938 | 82% | 676 [554–708] | |
| Calories burned from periods above sedentary level | 7629 | 5679 | 100% | 676 [554–708] | |
| Calories burned inclusive of BMR | 8279 | 6142 | 100% | 676 [554–708] | |
| Minutes spent fairly active | 7291 | 5450 | 100% | 676 [554–708] | |
| Minutes spent sedentary | 8196 | 6082 | 100% | 676 [554–708] | |
| Minutes spent very active | 7171 | 5370 | 100% | 676 [554–708] | |
| Minutes spent lightly active | 7628 | 5678 | 100% | 676 [554–708] | |
| Sensor features (Heart) | Daily resting heart rate | 9105 | 6810 | 81% | 492 [341–653] |
| Maximum daily heart rate variability | 1812 | 1407 | 0% | 363 [185–499] | |
| Minimum daily heart rate variability | 1812 | 1407 | 0% | 363 [185–499] | |
| Average daily heart rate variability | 1812 | 1407 | 0% | 363 [185–499] | |
| Sensor features (Sleep) | Total daily sleep time | 7473 | 5603 | 94% | 445 [240–629] |
| Total daily time spent in bed | 7473 | 5603 | 94% | 445 [240–629] | |
| Sleep efficiency of the main sleep | 7473 | 5603 | 94% | 445 [240–629] | |
| Sleep time of the main sleep | 7473 | 5603 | 94% | 445 [240–629] | |
| Anthropometrics | Body mass index | 8478 | 6303 | — | — |
| Self-reported height | 1673 | 1277 | — | — | |
| Body weight | 9240 | 6896 | — | — | |
| Body fat percentage | 4594 | 3431 | — | — | |
| Basal metabolic rate (BMR) only calories | 8279 | 6142 | — | — | |
| Demographic features | Self-reported gender | 10,494 | 7853 | — | — |
| Age at the time of test | 10,479 | 7841 | — | — |
The set of features for each category is reported in the table. The same individual may report multiple tests. The total number of individual COVID-19 tests is the number of tests with the corresponding feature value available for the analysis, after exclusion criteria. The number of corresponding unique individuals is also reported. The available days for Sensor Features represent the median number of days available for all the participants (IQR reported in brackets).