Materials and methods
Study design
Questionnaires prior to experimental procedures
Ambulatory sleep recordings
Objective sleep parameter (polysomnography) | Self-rated sleep parameter (evening/morning protocol) | |
---|---|---|
Time in bed (TIB) | Time period from “lights off” to “lights on” (oTIB, min) | Time period from “lights off” to “lights on” (TIB, min) |
Total sleep time (TST) | Time period from “lights off” to “lights on” minus wake (oTST, min) | Estimated total sleep time (sTST, min) |
Sleep efficiency index (SEI) | (oTST/oTIB) × 100; (oSEI, %) | (sTST/sTIB) × 100; (sSEI, %) |
Sleep onset latency (SOL) | Sleep onset latency stage 1: time period from “lights off” to stage 1 (oSOL, min) | Estimated time from “lights off” to falling asleep (sSOL, min) |
Wake after sleep onset (WASO) | Wake after sleep onset (oWASO, min) | Estimated total time awake during night (sWASO, min) |
Restfulness (VAS) | – | Visual analogue scale (VAS, morning): low values indicate high restfulness (0 = very restful, 100 = not restful) |
Self-rated sleep parameters
Statistical analysis
Results
Characteristics of participants
Parameter | Total sample (n = 397) | Analysis group (n = 335) | Dropouts/excluded (n = 62) | Analysis group vs. dropouts/excluded |
---|---|---|---|---|
Median (IQR) | Median (IQR) | Median (IQR) | p‑valuea | |
Age (years) | 45.0 (35.0, 55.5) | 45.0 (35.0, 56.0) | 41.0 (34.0, 55.3) | 0.426 |
BMI kg/m2 | 26.2 (23.6, 29.3) | 26.2 (23.6, 29.3) | 25.9 (23.3, 29.8) | 0.836 |
PSQI score | 5.0 (3.0, 6.0) | 5.0 (3.0, 6.0) | 4.0 (3.0, 6.0) | 0.816 |
ESS score | 8.0 (5.0, 10.0) | 7.0 (5.0, 10.0) | 9.0 (5.0, 10.3) | 0.224 |
SDS score | 32.0 (27.0, 36.0) | 32.0 (28.0, 36.0) | 31.0 (26.0, 35.5) | 0.633 |
SAS score | 30.0 (26.0, 34.0) | 30.0 (26.0, 34.0) | 29.0 (25.0, 34.3) | 0.467 |
n (%) | n (%) | n (%) | p‑valueb | |
Female | 202 (50.9) | 175 (52.2) | 27 (43.5) | 0.209 |
PSQI score >5 | 129 (32.5) | 108 (32.2) | 21 (34.4) | 0.737 |
ESS score >10 | 81 (20.4) | 66 (19.7) | 15 (24.2) | 0.420 |
SDS score >40 | 37 (9.3) | 27 (8.1) | 10 (16.1) | 0.045 |
SAS score >35 | 76 (19.1) | 62 (18.5) | 14 (22.6) | 0.454 |
MEQ—definite evening type (<31) | 1 (0.3) | 1 (0.3) | 0 (0.0) | 0.365 |
MEQ—moderate evening type (31–41) | 17 (4.3) | 13 (3.9) | 4 (6.5) | |
MEQ—indifferent type (42–58) | 178 (44.8) | 146 (43.6) | 32 (51.6) | |
MEQ—moderate morning type (59–69) | 158 (39.8) | 135 (40.3) | 23 (37.1) | |
MEQ—definite morning type (>69) | 43 (10.8) | 40 (11.9) | 3 (4.8) | |
Employment status | ||||
Employed (fulltime) | 161 (40.6) | 129 (38.5) | 32 (51.6) | 0.054 |
Part-time/not employed/training/school | 236 (59.4) | 206 (61.5) | 30 (48.4) |
Bedtimes and getting up times
Objective sleep parameter across weekdays
Sun | Mon | Tue | Wed | Thu | Fri | ||
---|---|---|---|---|---|---|---|
Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | p‑valuea | |
Objective sleep parameters | |||||||
Time in bed (oTIB, min) | 447.6 [389.4; 492.6] | 432.4 [391.6; 476.6] | 438.1 [392.0; 480.2] | 432.0 [392.4; 473.7] | 432.9 [389.8; 477.5] | 439.9 [396.4; 476.7] | <0.0001 |
Total sleep time (oTST, min) | 414.5 [360.0; 458.5] | 400.5 [359.3; 441.0] | 402.0 [360.3; 437.3] | 402.3 [359.5; 437.0] | 399.0 [361.0; 443.0] | 404.3 [363.8; 441.8] | 0.0151 |
Sleep efficiency index (oSEI, %) | 93.0 [90.3; 95.2] | 93.0 [90.0; 94.8] | 93.3 [90.7; 95.0] | 93.5 [90.6; 95.1] | 93.3 [90.5; 95.1] | 93.3 [90.3; 95.1] | 0.1786 |
Sleep onset latency (oSOL, min) | 9.8 [4.8; 18.7] | 10.4 [6.4; 16.2] | 9.9 [6.4; 15.6] | 9.9 [6.3; 15.3] | 8.7 [5.4; 16.5] | 8.7 [5.3; 14.3] | <0.0001 |
Wake after sleep onset (oWASO, min) | 23.7 [14.2; 36.3] | 22.4 [14.9; 36.4] | 23.7 [15.1; 33.8] | 21.3 [14.4; 33.4] | 21.4 [13.9; 32.8] | 22.0 [14.9; 35.2] | 0.2692 |
Self-rated sleep parameters | |||||||
Time in bed (sTIB, min) | 445.0 [389.5; 502.0] | 433.5 [391.3; 479.0] | 436.5 [388.0; 482.5] | 435.0 [390.0; 475.0] | 434.0 [389.3; 477.5] | 446.0 [397.5; 490.0] | <0.0001 |
Total sleep time (sTST, min) | 410.0 [360.0; 450.0] | 390.0 [360.0; 435.0] | 390.0 [360.0; 435.0] | 405.0 [360.0; 445.0] | 405.0 [360.0; 437.5] | 405.0 [360.0; 450.0] | <0.0001 |
Sleep efficiency index (sSEI, %) | 92.6 [83.5; 97.5] | 92.5 [86.3; 97.1] | 92.9 [86.4; 96.8] | 93.4 [87.9; 97.8] | 93.3 [88.5; 97.3] | 93.8 [88.1; 98.0] | 0.0110 |
Sleep onset latency (sSOL, min) | 10.0 [5.0; 22.5] | 12.5 [7.5; 25.0] | 12.5 [7.5; 22.5] | 10.0 [5.0; 21.3] | 10.0 [5.0; 20.0] | 10.0 [5.0; 17.5] | <0.0001 |
Wake after sleep onset (sWASO, min) | 10.0 [5.0; 30.0] | 12.5 [7.5; 30.0] | 12.5 [6.0; 22.5] | 10.5 [6.4; 22.5] | 10.3 [5.4; 20.0] | 10.0 [5.0; 22.8] | 0.0157 |
Restfulness (VAS) | 33.0 [22.0; 52.0] | 37.5 [26.3; 51.3] | 35.0 [24.0; 47.0] | 31.0 [21.0 45.5] | 33.0 [22.3; 45.5] | 31.0 [21.3; 43.5] | <0.0001 |
Sun | Mon | Tue | Wed | Thu | Fri | ||
---|---|---|---|---|---|---|---|
Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | Median [IQR] | p‑valuea | |
Objective sleep parameters | |||||||
Time in bed (oTIB, min) | 422.9 [374.4; 458.6] | 414.5 [369.6; 460.3] | 429.4 [368.6; 462.5] | 416.0 [369.6; 460.3] | 421.8 [377.6; 460.4] | 428.2 [386.3; 474.0] | 0.0304 |
Total sleep time (oTST, min) | 387.0 [349.6; 422.5] | 383.3 [345.8; 421.4] | 391.3 [347.3; 430.3] | 384.1 [345.5; 427.8] | 389.1 [353.1; 427.5] | 393.0 [356.8; 431.4] | 0.1062 |
Sleep efficiency index (oSEI, %) | 93.4 [90.8; 95.7] | 93.5 [90.9; 95.3] | 94.0 [91.9; 95.5] | 94.0 [92.0; 95.7] | 94.0 [91.7; 95.2] | 94.2 [91.4; 95.2] | 0.1186 |
Sleep onset latency (oSOL, min) | 9.0 [4.7; 16.6] | 8.4 [6.2; 14.0] | 8.1 [5.2; 13.1] | 8.4 [5.8; 11.8] | 7.4 [5.0; 11.8] | 7.6 [5.0; 11.3] | 0.0097 |
Wake after sleep onset (oWASO, min) | 20.8 [12.0; 33.0] | 19.0 [13.6; 29.3] | 18.6 [12.3; 28.5] | 18.1 [12.1; 24.7] | 17.7 [11.3; 28.3] | 18.4 [13.1; 28.2] | 0.0894 |
Self-rated sleep parameters | |||||||
Time in bed (sTIB, min) | 420.0 [374.0; 465.0] | 413.5 [372.0; 462.0] | 415.0 [370.0; 454.5] | 419.0 [380.0; 463.8] | 419.5 [372.5; 464.3] | 428.5 [391.8; 483.5] | 0.0197 |
Total sleep time (sTST, min) | 390.0 [348.8; 420.0] | 382.5 [345.0; 420.0] | 387.5 [345.4; 427.5] | 390.0 [345.0; 427.5] | 390.0 [338.8; 420.0] | 400.0 [360.0; 450.0] | 0.0145 |
Sleep efficiency index (sSEI, %) | 93.3 [87.3; 97.9] | 93.3 [87.5; 97.4] | 93.7 [87.4; 97.3] | 94.8 [89.4; 98.0] | 94.1 [90.3; 97.2] | 93.9 [89.2; 97.9] | 0.1702 |
Sleep onset latency (sSOL, min) | 10.0 [5.0; 20.0] | 10.0 [5.0; 20.0] | 10.0 [5.0; 15.0] | 7.5 [5.0; 13.8] | 7.5 [5.0; 12.5] | 7.5 [4.0; 12.5] | <0.0001 |
Wake after sleep onset (sWASO, min) | 10.0 [5.0; 30.0] | 12.5 [7.5; 22.5] | 10.0 [5.7; 17.5] | 10.0 [5.9; 25.0] | 10.0 [5.0; 20.0] | 8.8 [5.0; 22.0] | 0.1070 |
Restfulness (VAS) | 34.0 [24.0; 51.8] | 39.8 [26.5; 51.5] | 37.2 [23.6; 49.1] | 34.5 [21.5 46.9] | 32.0 [22.0; 46.0] | 31.0 [22.1; 42.0] | 0.0001 |