Table 1 Characteristics and descriptive statistics of the whole cohort

Age(year), mean ± s.d.

31.9 ± 6.3

32.4 ± 6.9

31.6 ± 5.8

0.39

BMI (kg/m²), mean ± s.d.

24.6 ± 3.3

24.1 ± 3.0

24.8 ± 3.5

0.39

Education, n (%)

  primary school

5 (2.6)

1 (1.1)

4 (3.7)

0.32

  junior high school

40 (20.5)

21 (23.9)

19 (17.8)

  High school

43 (22.1)

22 (25.0)

21 (19.6)

  College/University

107 (54.8)

44 (50.0)

63 (58.9)

Duration of infertility, n (%)

  1 year

106 (54.4)

47 (53.4)

59 (55.1)

0.35

  2 years

47 (24.1)

25 (28.4)

22 (20.6)

  ≥ 3 years

42 (21.5)

16 (18.2)

26 (24.3)

Type of infertility, n (%)

  Primary

117 (60.0)

49 (55.7)

68 (63.6)

0.26

  Secondary

78 (40.0)

39 (44.3)

39 (36.4)

Alcohol status, n (%)

  Nondrinkers

58 (29.7)

24 (27.3)

34 (31.8)

0.49

  drinkers

137 (70.3)

64 (72.7)

73 (68.2)

Smoking status, n (%)

  Nonsmokers

112 (57.4)

48 (54.5)

64 (59.8)

0.46

  Smokers

83 (42.6)

40 (45.5)

43 (40.2)

Semen parameters

  Abstinence time (days), mean ± s.d

4.3 ± 1.9

4.2 ± 1.9

4.3 ± 2.0

0.75

  Semen volume (ml), median (Q1, Q3)

2.9 (2.0, 4.0)

2.8 (1.9, 3.7)

3.0 (2.2,4.1)

0.04

  Sperm concentration (×10⁶/ml), median (Q1, Q3)

79.0 (37.0, 121.6)

66.4 (28.2, 106.0)

89.5 (54.5, 135.5)

0.01

  Progressive motility (%), median (Q1, Q3)

38.0 (18.7, 51.0)

33.8 (19.1, 45.1)

41.6 (16.7, 54.6)

0.02

  Total motility (%), median (Q1, Q3)

46.0 (22.4, 59.3)

40.8 (22.5, 55.2)

50.2 (21.4, 63.8)

0.03

  Normal morphology (%), median (Q1, Q3)

5.0 (4.0, 8.0)

5.0 (3.0, 7.0)

5.0 (4.0, 8.0)

0.35

  leukocytes (×10⁶/ml), median (Q1, Q3)

0.4 (0.1, 4.6)

4.3 (2.9, 6.5)

0.2 (0.1, 0.3)

< 0.001

  AsAs (%), median (Q1, Q3)

1.5 (0, 4.0) (n = 124)

1.0 (0, 4.0) (n = 48)

2.0 (1.0, 3.8) (n = 76)

0.99