Skip to main content

Table 2 Sleep problems and sleepiness while driving reported by Daily two shift and Alternating day shift bus drivers

From: Sleepiness while driving and shiftwork patterns among Korean bus drivers

Variables Daily two shift
(n = 128)
Alternating day shift
(n = 204)
p-value
N (%) or M ± SD N (%) or M ± SD
Sleep disorder diagnosed by a doctor 8 (6.3) 18 (8.8) 0.3956
Sleeping time on workdays (h)
  < 6 16 (12.5) 74 (36.3) <0.0001
 6–8 86 (67.2) 106 (52.0)  
  ≥ 8 26 (20.3) 24 (11.8)  
 M ± SD 6.6 ± 1.0 6.0 ± 1.3 <0.0001
Sleeping time on off-days (h)
  < 6 3 (2.3) 15 (7.4) 0.0014
 6–8 35 (27.3) 85 (41.7)  
  ≥ 8 90 (70.3) 104 (51.0)  
 M ± SD 8.2 ± 1.4 7.7 ± 1.6 0.0013
Karolinska sleepiness scale (KSS, M ± SD)
 First 3.3 ± 1.8 3.1 ± 1.9 0.3346
 Morning 3.7 ± 1.8 3.4 ± 1.7 0.1355
 Post-lunch 3.9 ± 1.8 5.4 ± 2.0 <0.0001
 Afternoon 3.0 ± 1.5 5.0 ± 2.0 <0.0001
 Last 3.3 ± 1.7 5.0 ± 2.3 <0.0001
Severe sleepiness while driving (KSS ≥ 7)
 First 8 (6.3) 15 (7.4) 0.7001
 Morning 11 (8.6) 14 (6.9) 0.5607
 Post-lunch 13 (10.2) 81 (39.7) <0.0001
 Afternoon 2 (1.6)a 63 (30.9) <0.0001
 Last 6 (4.7) 64 (31.4) <0.0001
  1. M Mean, SD Standard Deviation
  2. aBy Fisher’s exact test