Table 3.
Sleep measures and group-level discrepancies in the sample of healthy sleepers and adolescents with insomnia symptoms.
| Fitbit Charge 3™ Mean (SD) |
PSG Mean (SD) |
Bias Mean (SD) [95% CI] |
Lower LOA [95% CI] |
Upper LOA [95% CI] |
||
|---|---|---|---|---|---|---|
| TST (min) | Healthy Sleepers | 396.76 (51.40) | 407.72 (53.03) | −10.96 (15.65) [−17.42, −4.50]* |
−41.63 [−52.82, −30.44] |
19.71 [8.52, 30.90] |
| Insomnia Symptoms | 410.21 (60.17) | 426.46 (64.46) | −16.25 (12.55) [−23.17, −9.50]* |
−40.85 [−47.72, −34.05] |
8.35 [1.68, 15.10] |
|
| SE (%) | Healthy Sleepers | 89.46 (4.23) | 91.89 (4.02) | −2.43 (3.51) [−3.87, −.98]* |
−9.30 [−11.80, −6.79] |
4.44 [1.94, 6.95] |
| Insomnia Symptoms | 86.98 (5.96) | 90.42 (6.83) | 14.32 - .20 × PSG b0 = [3.19, 70.71], b1 = [−.80, −.01]* |
Bias - 4.58 [1.70, 5.71] |
Bias + 4.58 [1.70, 5.71] |
|
| SOL (min) | Healthy Sleepers | 9.36 (7.39) | 7.40 (7.46) | 1.96 (5.16) [−.17, 4.09] |
Bias - 2.46(1.10 + .33 × PSG) c0 = [−.17, 2.37], c1 = [.20, .45]* |
Bias + 2.46(1.10 + .33 × PSG) c0 = [−.17, 2.37], c1 = [.20, .45]* |
| Insomnia Symptoms | 13.62 (8.99) | 16.25 (22.79) | −2.62 (17.64) [−13.50, 5.54] |
−37.21 [−47.66, −29.33] |
31.96 [21.12, 39.83] |
|
| WASO (min) | Healthy sleepers | 37.46 (19.99) | 28.46 (14.91) | 9.00 (15.47) [2.61, 15.39]* |
−21.32 [−32.38, −10.26] |
39.32 [28.26, 50.38] |
| Insomnia Symptoms | 47.00 (22.60) | 28.12 (20.69) | 18.88 (15.48) [10.75, 27.62]* |
−11.46 [−19.59, −2.76] |
49.21 [41.09, 57.76] |
|
| Light (min) | Healthy Sleepers | 241.89 (34.49) | 225.41 (43.26) | 170.26 - .68 × PSG b0 = [101.18, 239.35], b1 = [−.98, −.38]* |
Bias - 62.00 [49.74, 80.23] |
Bias + 62.00 [49.74, 80.23] |
| Insomnia Symptoms | 234.62 (34.51) | 230.21 (35.78) | 4.42 (35.93) [−15.46, 23.83] |
−66.00 [−86.79, −47.59] |
74.84 [54.88, 93.63] |
|
| Deep (min) | Healthy Sleepers | 72.2 (21.26) | 94.65 (24.28) | 56.93 - .84 × PSG b0 = [22.32, 91.54], b1 = [−1.19, −.48]* |
Bias - 40.96 [34.16, 52.17] |
Bias + 40.96 [34.16, 52.17] |
| Insomnia Symptoms | 78.04 (29.44) | 103.58 (25.20) | −25.54 (25.01) [−38.29, −11.04]* |
−74.55 [−87.05, −60.22] |
23.47 [10.93, 37.68] |
|
| REM (min) | Healthy Sleepers | 82.15 (28.63) | 80.11 (23.94) | 2.04 (21.53) [−6.48, 10.55] |
−40.16 [−54.91, −25.41] |
44.23 [29.48, 58.98] |
| Insomnia Symptoms | 97.54 (46.87) | 92.67 (28.05) | 4.88 (30.14) [−11.58, 20.79] |
−54.19 [−71.03, −38.28] |
63.94 [47.32, 79.82] |
TST, Total sleep time; SE, Sleep efficiency; SOL, Sleep onset latency; WASO, Wake after sleep onset; Light, “light” sleep duration (i.e., PSG-derived N1 + N2); Deep, “deep” sleep duration (i.e., PSG-derived N3); REM, Rapid-Eye-Movement sleep; SD, standard deviation; PSG, polysomnography; LOA, limit of agreement; CI, confidence intervals (computed using percentile bootstrap for the group with insomnia symptoms due to skewed distributions and small sample size)
cases showing a significant bias, proportional bias or heteroscedasticity. When a proportional bias was detected, a linear model predicting the discrepancies by the corresponding PSG measures was specified, and 95% CI were reported for the model’s intercept (b0) and slope (b1). When heteroscedasticity was detected, a linear model predicting the absolute residuals of the previous model by PSG-derived measures was specified, and 95% CI were reported for the model’s intercept (c0) and slope (c1).