Table 3.
Smartphone GPS and accelerometer data collection compliance at the participant day level by phone operating system (OS) for the Beiwe Smartphone Substudy of the Nurses’ Health Study 3 and Growing Up Today Study (N=870,525 total potential data collection days).
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Overall, n (%) | By phone OS, n (%) | |||
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Android (n=234,695) | iOS (n=633,640) | Botha (n=2190) | |
| Participant day–level compliance rates—GPS data | |||||
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Valid daysb | 351,520 (40.38) | 90,410 (38.52) | 259,838 (41.01) | 1272 (58.08) |
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Invalid days | 92,270 (10.6) | 9890 (4.21) | 82,046 (12.95) | 334 (15.25) |
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Noncollection daysc | 426,735 (49.02) | 134,395 (57.26) | 291,756 (46.04) | 584 (26.67) |
| Participant day–level compliance rates—accelerometer data | |||||
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Valid daysb | 348,394 (40.02) | 91,960 (39.18) | 255,333 (40.3) | 1101 (50.27) |
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Invalid days | 113,090 (12.99) | 24,367 (10.38) | 88,166 (13.91) | 557 (25.43) |
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Noncollection daysc | 409,041 (46.99) | 118,368 (50.43) | 290,141 (45.79) | 532 (24.29) |
aSome participants switched smartphones during the 1-year data collection period, which resulted in a different OS.
bA valid day was defined as one with at least 600 valid minutes (10 valid hours) per day for GPS and accelerometer data. The participant day–level compliance was calculated as the percentage of valid days out of the total potential data collection days. Potential data collection days for each participant were defined as 365 days from the date the participant registered on the app.
cMissing days were defined as days without data. In this study, the primary reason for missing days was attrition (ie, the app was deleted from a participant’s phone before the 1-year study completion date because the participant unenrolled from the substudy). Another reason was sensor noncollection, which could be due to a participant forgetting to charge their phone or disabling the GPS or a major update from the OS causing the Beiwe app to malfunction temporarily, among other reasons.