Table 1.
Sleep Variables, Mean Differences, and Epoch-by-Epoch Comparisons
| Value (SD) | ||||
|---|---|---|---|---|
| Measure | TST (min) | SE (%) | SOL (min) | WASO (min) |
| PSG | 457.8 (80.8) | 84.4 (7.7) | 19.2 (22.7) | 68.3 (44.2) |
| AW-2 | 498.3 (20.3) | 91.4 (3.1) | 5.8 (7.7) | 41.2 (17.0) |
| FBF-N | 503.7 (89.6) | 92.5 (3.5) | 17.2 (14.2) | 24.3 (19.1) |
| FBF-S | 371.5 (72.0) | 68.4 (8.8) | 30.7 (28.6) | 143.1 (62.6) |
| Bland-Altman Mean Difference (p-value) | ||||
| Comparison | TST (min) | SE (%) | SOL (min) | WASO (min) |
| AW-2 v. PSG | 40.6 (.0004) | 7.0 (.0003) | −13.5 (.012) | −27.1 (.005) |
| FBF-N v. PSG | 46.0 (<.0001) | 8.1 (<.0001) | −2.0 (.72) | −44.0 (<.0001) |
| FBF-N v. AW-2 | 5.4 (.08) | 1.1 (.042) | 11.5 (.0003) | −16.9 (<.0001) |
| FBF-S v. PSG | −86.3 (<.0001) | −16.0 (<.0001) | 11.5 (.012) | 74.8 (<.0001) |
| FBF-S v. AW-2 | −126.8 (<.0001) | −22.9 (<.0001) | 24.9 (.0006) | 101.9 (<.0001) |
| Sensitivity, Specificity, and Accuracy (SD) | ||||
| Comparison | Sensitivity | Specificity | Accuracy | |
| AW-2 v. PSG | 0.97 (0.02) | 0.31 (0.15) | 0.87 (0.06) | |
| FBF-N v. PSG | 0.98 (0.02) | 0.35 (0.13) | 0.88 (0.05) | |
| FBF-S v. PSG | 0.78 (0.09) | 0.80 (0.17) | 0.78 (0.08) | |
Sleep variables of interest derived from Polysomnography (PSG), Actiwatch-2 (AW-2), Fitbit Flex Normal Setting (FBF-N), and Fitbit Flex Sensitive Setting (FBF-S). TST = Total Sleep Time (minutes); SE = Sleep Efficiency (percentage); SOL = Sleep Onset Latency (minutes); WASO = Wake After Sleep Onset (minutes). Values reported as mean ± standard deviation. Mean difference between comparisons derived from Bland-Altman analysis with corresponding p-value reported for each variable of interest. Sensitivity (ability to detect PSG-scored sleep epochs), Specificity (ability to detect PSG-scored wake epochs), and Accuracy (ability to detect PSG-scored sleep and wake epochs) mean values with standard deviation are reported for each device.