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Table 1 Biographical variables, life habits, and number of night and evening shifts/month among the JFCT members

From: Sleep patterns among shift-working flight controllers of the International Space Station: an observational study on the JAXA Flight Control Team

  DW (n = 8) ONEW (n = 14) Night shift worker One-factor ANOVA or Fisher’s exact test
SWSD− (n = 16) SWSD+ (n = 14) F value p value
Number of subjects who had symptoms of insomnia or excessive wake time sleepiness 0 7 (50 %) 0 14 (100 %)   
Age (years) 37.5 ± 7.6 39.8 ± 5.5 37.8 ± 5.8 38.1 ± 6.8 0.346 0.792
Number of female subjects 3 2 1 0   0.043
BMI 21.2 ± 2.2 22.1 ± 2.3 22.0 ± 1.6 21.8 ± 3.2 0.26 0.854
Length of experience as a flight controller (years) 2.2 ± 2.0 4.3 ± 0.9 3.8 ± 1.3 3.8 ± 1.2 1.886 0.145
One-way commuting time (min) 18 ± 12 23 ± 9 25 ± 18 28 ± 32 0.442 0.724
Number of subjects living alone 3 (38 %) 0 3 (19 %) 4 (29 %)   0.077
Number of subjects living with an infant 4 (50 %) 9 (64 %) 4 (25 %) 5 (36 %)   0.162
Diurnal score 16.0 ± 5.1 15.8 ± 2.9 16.3 ± 3.3 15.6 ± 2.3 0.098 0.961
Habitual exerciser 1 (13 %) 5 (36 %) 6 (40 %) 4 (29 %)   0.682
Habitual drinker 1 (13 %) 3 (21 %) 2 (13 %) 2 (14 %)   0.951
Smoker 0 0 1 (7 %) 2 (14 %)   0.473
Heavy caffeine drinker 1 (13 %) 2 (14 %) 4 (25 %) 1 (7 %)   0.716
Days of night shift/month 0 1.4 ± 0.9 4.9 ± 1.3 4.3 ± 1.4 49.44 <0.0001
Days of evening shift/month 0 4.0 ± 3.8 3.4 ± 1.5 3.6 ± 1.6 5.833 0.002
  1. The values denote the mean ± standard deviation or the number of subjects and percentages. p values denote the results of the one-factor ANOVA or Fisher’s exact test among the subject groups