Table 5.

Average length of each night shift and risk of NAFLD

Variables	Average length of each night shift during night shift periods				Ptrend	Mediation effect (%) (95% CI)
	None	< 8 h	8–12 h	> 12 h
Case/Sample	333/57003	48/5982	62/6337	59/5737
Incidence rate (/100,000 person years)	48.29	66.63	81.03	85.02
Model 1	1.00	1.31 (0.97–1.78)	1.67 (1.27–2.18)	1.74 (1.32–2.3)	< 0.001
Model 2	1.00	1.18 (0.87–1.60)	1.47 (1.11–1.93)	1.61 (1.22–2.13)	< 0.001
Model 3	1.00	1.17 (0.87–1.57)	1.38 (1.06–1.80)	1.53 (1.17–2.00)	< 0.001
Mediation model	1.00	1.06 (0.79–1.42)	1.27 (0.97–1.66)	1.38 (1.06–1.81)	0.004	24.2 (12.0–42.7) P < 0.001

Model 1 was adjusted for age, sex, and ethnicity (white or others)

Model 2 was model 1 plus further adjustment for Townsend deprivation index, education level (university/college degree or others), household income (less than £18,000, £18,000 to £30,999, £31,000 to £51,999, £52,000 to £100,000, greater than £100,000, or do not know/prefer not to answer), self-reported smoking status (never, former or current smoker), self-reported frequency of alcohol intake (daily/almost daily, 1–4 times a week, 1–3 times a month, or special occasions only/never), and physical activity level (< 600, 600–3000, > 3000 MET minutes per week, or missing)

Model 3 was model 2 plus further adjustment for diabetes, hypertension, and PRS for NAFLD

The mediation model was adjusted for BMI separately in addition to model 3, and the mediation effect was calculated