Sleep Disorders

Research Article

The Impact of Sleep Timing, Sleep Duration, and Sleep Quality on Depressive Symptoms and Suicidal Ideation amongst Japanese Freshmen: The EQUSITE Study

Table 2

Sleep behaviours according to depressive symptoms and suicidal ideation.
 TotalNondepressed
()		Depressed
()		 valueNo suicidal ideation ()Suicidal ideation
()		 value
  (%) (%) (%) (%) (%)
Bedtime       
 23:30 or earlier287 (14.4)223 (15.0)64 (12.6)0.01274 (14.6)13 (11.3)0.04
 23:30–00:30 860 (43.2)659 (44.3)201 (39.6) 821 (43.7)39 (33.9) 
 00:30–01:30 663 (33.3)482 (32.5)181 (35.7) 616 (32.8)47 (40.9) 
 Later than 01:30 182 (9.1)121 (8.1)61 (12.0) 166 (8.8)16 (13.9) 
Wake time       
 06:00 or earlier935 (46.9)718 (48.4)217 (42.8)0.15882 (47.0)53 (46.1)0.65
 06:00–07:00 762 (38.3)555 (37.4)207 (40.8) 717 (38.2)45 (39.1) 
 07:00–08:00242 (12.2)176 (11.9)66 (13.0) 230 (12.3)12 (10.4) 
 Later than 08:0053 (2.7)36 (2.4)17 (3.4) 48 (2.6)5 (4.3) 
Sleep-onset latency      0.17
 <30 min1526 (76.6)1170 (78.8)356 (70.2)<0.011444 (76.9)82 (71.3) 
 30 min466 (23.4)315 (21.2)151 (29.8) 433 (23.1)33 (28.7) 
Sleep duration       
 6 h or less551 (27.7)421 (28.4)130 (25.6)0.34510 (27.2)41 (35.7)0.23
 6-7 h932 (46.8)699 (47.1)233 (46.0) 886 (47.2)46 (40.0) 
 7-8 h417 (20.9)298 (20.1)119 (23.5) 395 (21.0)22 (19.1) 
 >8 h92 (4.6)67 (4.5)25 (4.9) 86 (4.6)6 (5.2) 
Sleep quality   <0.01  <0.0001
 Good sleep 1329 (66.7)1070 (72.1)259 (51.1) 1278 (68.1)51 (44.3) 
 Poor sleep663 (33.3)415 (28.0)248 (48.9) 599 (32.0)64 (55.7)