Table 1 Participants’ characteristics
From: Development and validation of the Japanese version of the Bedtime Procrastination Scale (BPS-J)
|  | Time 1 n = 574 | Time 2 n = 280 | ||||
|---|---|---|---|---|---|---|
Median or n | SD or % | Median or n | SD or % | |||
Sex | ||||||
 Male | 287 | 50.00% | 144 | 51.40% |  |  |
 Female | 287 | 50.00% | 136 | 48.60% |  |  |
Age (years) | 45.00 | 33.00 – 55.00 | 45.00 | 33.00 – 55.00 |  |  |
Self-control scale | 36.00 | 30.00 – 41.00 | 37.00 | 30.00 – 41.00 | χ2 = 5.69 | p = 0.02 |
General procrastination scale | 34.00 | 26.75 – 39.00 | 34.00 | 25.50 –39.50 | χ2 = 1.56 | p = 0.21 |
Feeling fatigue (days per week) | 2.00 | 0.00 – 3.00 | 1.00 | 0 – 3 | χ2 = 8.03 | p = 0.005 |
 0 days | 168 | 29.30% | 86 | 30.70% | z =—0.23 | p = 0.82 |
 1 – 2 days | 229 | 39.90% | 107 | 38.20% |  | 229 |
 3 – 4 days | 92 | 16.0% | 40 | 14.30% |  |  |
 5 – 6 days | 54 | 9.40% | 30 | 10.70% |  |  |
 7 days | 31 | 5.40% | 17 | 6.10% |  |  |
Feeling sleep loss (days per week) | 2.00 | 0.00 – 3.00 | 2.00 | 0 – 2 | χ2 = 0.63 | p < 0.001 |
 0 days | 168 | 29.30% | 81 | 28.90% | z =—3.27 | p < 0.001 |
 1 – 2 days | 196 | 34.10% | 87 | 31.10% |  |  |
 3 – 4 days | 103 | 17.90% | 51 | 18.20% |  |  |
 5 – 6 days | 75 | 13.10% | 44 | 15.70% |  |  |
 7 days | 32 | 5.60% | 17 | 6.10% |  |  |
Viewing bedtime procrastination as a problem | ||||||
 1 not at all | 86 | 15.00% | 40 | 14.30% | z =—0.36 | p = 0.72 |
 2 | 100 | 17.40% | 52 | 18.60% |  |  |
 3 | 165 | 28.70% | 88 | 31.40% |  |  |
 4 | 175 | 30.50% | 75 | 26.80% |  |  |
 5 very much | 48 | 8.40% | 25 | 8.90% |  |  |
Sleep duration on workdays | ||||||
 Less than 5 h | 35 | 6.10% | 15 | 5.40% | z =—0.002 | p = 0.99 |
 Less than 6 h | 570 | 34.00% | 94 | 33.60% |  |  |
 Less than 7 h | 210 | 36.60% | 106 | 37.90% |  |  |
 Less than 8 h | 108 | 18.80% | 50 | 17.90% |  |  |
 Less than 9 h | 22 | 3.80% | 11 | 3.90% |  |  |
 Less than 10 h | 3 | 0.50% | 2 | 0.70% |  |  |
 10 h and over | 1 | 0.20% | 2 | 0.70% |  |  |
Munich ChronoType Questionnaire | ||||||
 Sleep duration on workdays | 390.00 | 350.00 – 440.00 | 398.50 | 355.00 – 440.75 | χ2 = 1.83 | p = 0.18 |
 Sleep duration on work-free days | 445.00 | 390.00 – 495.00 | 445.00 | 385.00 – 497.00 | χ2 = 1.28 | p = 0.26 |
 Midsleep on workdays | 3:00 | 2:22 – 3:38 | 3:02 | 2:22 – 3:45 | χ2 = 0.07 | p = 0.80 |
 Midsleep on work-free days | 3:35 | 2:50 – 4:32 | 3:39 | 2:47 – 4:35 | χ2 = 0.69 | p = 0.41 |
 Absolute social jetlag (minutes) | 35.00 | 7.00 – 67.00 | 30.00 | 4.25 – 62.00 | χ2 = 0.004 | p = 0.95 |
 Absolute social jetlag ≥ 120 min | 51 | 8.90% | 19 | 6.80% | z =—0.23 | p = 0.82 |
 Weekly sleep loss (minutes) | 42.00 | 0.00 – 120.00 | 42.00 | 0.00 – 128.00 | χ2 = 0.63 | p = 0.43 |
 Work start time | 8:40 | 8:15 – 9:00 | 8:45 | 8:25 – 9:00 | χ2 = 0.06 | p = 0.81 |
 Work end time | 17:30 | 17:00 – 18:30 | 17:40 | 17:00 – 18:30 | χ2 = 0.17 | p = 0.68 |
 Working time (minutes) | 540.00 | 540.00 – 570.00 | 540.0 | 510.0 0– 582.50 | χ2 = 0.22 | p = 0.64 |