Table 5 Odds ratio and 95 % CI for poor sleep quality based on direction of shift rotation in subgroups

Age (years)

<0.001

 <30

Reference

1.89 (1.46–2.45)

 ≥30

Reference

2.60 (1.77–3.83)

BMI (kg/m²)

0.423

 18.5–24.9

Reference

1.84 (1.42–2.40)

 <18.5

Reference

2.56 (1.10–5.96)

 ≥25

Reference

2.19 (1.48–3.24)

Duration of shift work

0.197

 <5 years

Reference

1.78 (1.34–2.36)

 5–9 years

Reference

2.48 (1.63–3.77)

 ≥10 years

Reference

2.07 (1.19–3.60)

Weekly working hours

0.417

 <41 h

Reference

1.73 (1.03–2.88)

 41–51 h

Reference

1.96 (1.48–2.59)

 ≥52 h

Reference

1.82 (1.19–2.79)

Smoking status

0.566

 Non-smoker

Reference

1.95 (1.51–2.53)

 Ex-smoker

Reference

1.99 (1.38–2.88)

 Current smoker

Reference

5.36 (0.43–67.26)

Alcohol consumption

0.508

 Non-drinker

Reference

1.76 (1.20–2.58)

 Regular drinker

Reference

1.91 (1.46–2.49)

 Heavy drinker

Reference

3.32 (1.55–7.13)

Physical activity

0.427

 Sufficient exercise

Reference

1.97 (1.40–2.78)

 Insufficient exercise

Reference

1.94 (1.49–2.53)