Table 3 Development of NAFLD plus intermediate/high probability of advanced fibrosis based on NFS according to the working hour category in men and women.

From: Long working hours and increased risks of lean non-alcoholic fatty liver disease among Korean men and women

Categories of working hours

PY

Incident cases

Incidence rate (Cases per 1000 PY)

Age-adjusted HR (95% CI)

Multivariable-adjusted HR (95% CI)a

HR (95% CI)b in a model using time-dependent variables

Total

 35–40 h

42444.3

65

1.53 (1.20–1.95)

1.00 (reference)

1.00 (reference)

1.00 (reference)

 41–52 h

100611.6

153

1.52 (1.30–1.78)

1.16 (0.86–1.58)

1.49 (0.81–2.74)

1.49 (1.06–2.10)

 ≥ 53 h

46728

87

1.86 (1.51–2.30)

1.30 (0.93–1.81)

1.43 (0.69–2.96)

1.39 (0.88–2.19)

 p for trend

   

0.185

0.869

0.116

Men

 35–40 h

13239.2

47

3.55 (2.67–4.72)

1.00 (reference)

1.00 (reference)

1.00 (reference)

 41–52 h

55254.3

137

2.48 (2.10–2.93)

1.23 (0.87–1.74)

1.79 (0.87–3.64)

1.66 (1.13–2.43)

 ≥ 53 h

30311.4

78

2.57 (2.06–3.21)

1.33 (0.91–1.94)

1.96 (0.87–4.42)

1.54 (0.94–2.51)

 p for trend

   

0.303

0.598

0.067

Women

 35–40 h

29205.1

18

0.62 (0.39–0.98)

1.00 (reference)

1.00 (reference)

1.00 (reference)

 41–52 h

45357.3

16

0.35 (0.22–0.58)

0.87 (0.44–1.73)

0.87 (0.22–3.48)

–

 ≥ 53 h

16417.1

9

0.55 (0.29–1.05)

1.05 (0.47–2.35)

0.365 (0.007–17.458)

–

 p for trend

   

0.811

0.460

–

  1. NAFLD, non-alcoholic fatty liver disease; NFS, nonalcoholic fatty liver disease fibrosis score; PY, person-years; HR, hazard ratio; CI, confidence interval.
  2. p = 0.058 for the overall interaction between sex and working hour category for incident NAFLD plus fibrosis based on NFS (time-dependent model).
  3. aEstimated from parametric proportional hazard models with age, year of visit, center, sex, marital status, income level, education level, stress level, hypertension, depression, smoking status, alcohol consumption, physical activity level, sitting time, and sleep duration.
  4. bEstimated from parametric proportional hazard models with center, sex, marital status, and education level as time-fixed variables and working hours, stress level, hypertension, depression, smoking status, alcohol consumption, physical activity level, sitting time, and sleep duration as a time-dependent variable.
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