Table 1 Baseline characteristics of the study participants (N = 977)

Age (year)

31.72 ± 7.97

 Range (year)^a

18–55

 Missing

37

Age group (year)

 18–20

46 (4.89)

 21–29

371 (39.47)

 30–39

341 (36.28)

 ≥ 40

182 (19.36)

 Missing

37

Race

 Han

957 (97.95)

 Others

20 (2.05)

Education

 Primary school

1 (0.10)

 Junior high school

4 (0.41)

 High/technical school

72 (7.37)

 College

133 (13.61)

 Undergraduate

210 (21.49)

 Postgraduate and above

557 (57.01)

Working hours

 Regular day shift

548 (56.09)

 Regular night shift

28 (2.87)

 Irregular night shift

49 (5.02)

 Regular shift

79 (8.09)

 Irregular shift

71 (7.27)

 Not working at present

202 (20.68)

 Height (cm)

162.27 ± 4.96

 Body weight (kg)

58.62 ± 9.13

 BMI (kg/m²)

22.27 ± 3.44

BMI group (kg/m²)

 Underweight (BMI < 18.5)

107 (10.95)

 Normal weight (BMI = 18.5–24.9)

697 (71.34)

 Overweight (BMI = 25–29.9)

139 (14.23)

 Obesity (BMI ≥ 30)

34 (3.48)