Table 5.
Features of the data used for artificial intelligence (AI) development in the included studies (N=69).
| Feature | Values | References | |
| Data set size, mean (SD; range) | 168,022.5 (428,843.2; 168-1,570,144) | [22,23,28,37,41,44,45,51,58,60-62,70,73] | |
| Data set source, n (%) | |||
| Open | 19 (28) | [19,20,28,31,32,34,36,42,43,47,48,62,65,68-71,74,86] | |
| Closed | 50 (72) | [21-27,29,30,33,35,37-41,44-46,49-61,63,64,66,67,72,73,75-85,87] | |
| Data types, n (%) | |||
| WDa based | 41 (59) | [20-22,27,29,31-36,38,39,41-48,53-56,58,61,62,65,67,69-71,73,75,76,78-80,82,87] | |
| WD based and self-reported | 12 (17) | [19,26,28,30,49,51,52,57,68,81,85,86] | |
| WD based and non-WD based | 9 (13) | [23,25,40,50,59,66,72,74,84] | |
| WD based, non-WD based, and self-reported | 7 (10) | [24,37,60,63,64,77,83] | |
| Data input to AI algorithmb, n (%) | |||
| Physical activity data | 53 (77) | [19,20,23-27,30-32,34-38,41-51,54-57,59,60,62-74,76,77,79,81,83-86] | |
| Sleep data | 27 (39) | [23-26,30,33,37,38,41,46,49-52,57,59,60,63,64,66,73,74,77,79,81,83,84] | |
| Heart rate data | 26 (38) | [23,26,27,29-31,40,50,51,58-61,63,64,66,72,75,77-81,83,85,87] | |
| Mental health measures | 14 (20) | [24,26,30,37,46,49,50,52,57,60,64,77,81,85] | |
| Social interaction data | 10 (14) | [23-25,37,59,60,66,72,83,84] | |
| Location data | 10 (14) | [23,25,37,50,59,64,66,74,83,84] | |
| Smartphone use data | 10 (14) | [23,25,37,59,60,64,66,74,83,84] | |
| Electrodermal activity data | 10 (14) | [27,37,40,58,61,66,72,75,78,85] | |
| Skin temperature data | 5 (7) | [27,75,78,79,85] | |
| Demographic data | 5 (7) | [30,52,57,68,85] | |
| Electroencephalograph data | 4 (6) | [21,22,53,87] | |
| Light exposure | 4 (6) | [26,46,60,79] | |
| Audio data | 4 (6) | [39,44,54,85] | |
| Others | 17 (25) | [24,28,30,37,49,52,57,60,63,66,72-74,77,81,82,85] | |
| Number of featuresc, n (%) | |||
| 1-10 | 33 (48) | [19,21-25,27,34-40,43,46,47,50,54-58,67,69-72,75,78,82,83,87] | |
| 11-20 | 16 (23) | [23,26,28,30,33,45,48,51-53,57,61,68,72,76,86] | |
| 21-30 | 6 (9) | [44,52,60,63,73,85] | |
| 31-40 | 6 (9) | [23,34,38,50,66,73] | |
| 41-50 | 6 (9) | [23,41,64,73,77,80] | |
| >50 | 8 (12) | [23,27,59,73,74,79,81,84] | |
| Not reported | 8 (12) | [20,29,31,32,42,49,62,65] | |
aWD: wearable device.
bThe number of studies does not add up, as many studies used >1 data input.
cThe number of studies does not add up, as several studies used various numbers of features.