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Table 3 Sociodemographic and sleep characteristics and lifestyle in the groups with sleep problems

From: Impact of sleep problems on daytime function in school life: a cross-sectional study involving Japanese university students

 Insomnia
(n = 257)
Without Insomnia
(n = 754)
BIISS
(n = 28)
Without BIISS
(n = 916)
DSWP
(n = 20)
Without DSWP
(n = 936)
BIISS + DSWP
(n = 46)
Without BIISS + DSWP
(n = 898)
Age (y)19.8 ± 1.219.6 ± 1.2 a20.0 ± 1.219.7 ± 1.219.8 ± 1.019.7 ± 1.219.9 ± 1.019.7 ± 1.2
Sex
 Female (%)797810079 a70808779
Grade
 Freshman (%)3137253625362036
 Sophomore (%)2423252315232822
 Junior (%)3027322750273727
 Senior (%)1614181510151515
Living alone
 Yes (%)2121022 a5520 a1721
Commute time (min)59.6 ± 33.459.5 ± 34.485.4 ± 25.158.5 ± 33.5 a23.2 ± 20.060.0 ± 33.3 a66.2 ± 34.258.9 ± 33.5
School hours (h)6.9 ± 1.97.0 ± 1.87.4 ± 1.47.0 ± 1.86.1 ± 1.67.0 ± 1.8 a6.8 ± 2.07.0 ± 1.8
Class start time (h:m)9:18 ± 0:469:20 ± 0:468:59 ± 0:269:18 ± 0:45 a10:04 ± 1:119:17 ± 0:44 a9:22 ± 0:519:18 ± 1:36
Class closing time (h:m)16:11 ± 1:3916:17 ± 1:3516:22 ± 1:2216:15 ± 1:3716:07 ± 1:5716:15 ± 1:3616:10 ± 1:3916:16 ± 1:37
Club activities
 Yes (%)3241 a1439 a45382239 a
Part-time job
 Yes (%)6568686675667865
Exercise habit
 Yes (%)46492549 a50473349 a
Alcohol consumption
 Yes (%)4741574255425942 a
Smoking
 Yes (%)6545205 a45
Self-rated health status
 Poor (%)4122 a252720273926
Stress
 Yes (%)5641 a464545456544 a
Duration of nap
  < 10 min (%)2731313020301531
 10–29 min (%)3036353445343734
 30–59 min (%)2219191910202419
 ≥ 1 h (%)2113 b151525152415
Frequency of dreaming during nap
 Often (%)1812 b111410142613 b
 Sometimes (%)5353645260525253
 Not (%)3035253330332234
Sleep-related symptoms
 Difficulty initiating sleep (%)7610 a252630263926 a
 Difficulty maintaining sleep (%)245 a710510139
 Early morning awakening (%)154 a460646
 Difficulty awakening (%)4251 a43498049 a7448 a
 Hypnagogic hallucination (%)2715 a321815193518 a
 Sleep paralysis (%)1510 a111215112011
 REM parasomnia [7] (%)5747 a574960496149
 NREM parasomnia [8] (%)2415 a14173516 a2416
  1. asignificantly difference between the students with the sleep problem and without the sleep problem
  2. bsignificantly higher than other students by residual analysis (adjusted residual ≥1.96)
  3. BIISS Behaviorally induced insufficient sleep syndrome, DSWP Delayed sleep-wake phase
  4. REM Rapid eye movement, NREM Non-rapid eye movement
  5. REM parasomnia: nightmare and / or acting out their dreams
  6. NREM parasomnia: night terrors, defective awakening, and / or sleep walking