Table 1 General characteristics of the study population

Age (year) Mean (SD)

26.6 (4.2)

29.9 (6.2)

29.2 (7.2)

32.3 (5.6)

<0.001^a

BMI (Kg/m²) Mean (SD)

23 (0.8)

23 (2.3)

22.7 (1.0)

23.5 (0.9)

0.002^a

SBP (mmHg) Mean (SD)

125.6 (10.5)

121.2 (13.1)

125.2 (13.3)

129 (13.9)

0.001^a

DBP (mmHg) Mean (SD)

72.7 (9.6)

75.8 (47)

71 (12)

74 (13.8)

0.5861^a

 Education level n (%)

<0.001^b

 Primary school

1 (0.9)

3 (2.8)

1 (0.9)

0 (0.0)

 High school

109 (99.1)

97 (90.7)

93 (91.2)

2 (1.9)

 University

0 (0.0)

7 (6.5)

8 (7.9)

104 (98.1)

Working year n (%)

<0.001^b

 <5

74 (67.3)

38 (35.5)

81 (79.4)

74 (69.8)

 ≥5

36 (32.7)

69 (64.5)

21 (20.6)

32 (30.2)

Smoking status n (%)

<0.001^b

 Never

9 (8.1)

17 (15.8)

50 (49.0)

74 (69.8)

 Current

87 (79.0)

76 (71.0)

41 (40.1)

28 (26.4)

 Passive smoking at workplace

96 (87.2)

88 (82.2)

80 (78.4)

43 (40.5)

<0.001^b

Alcohol consumption n (%)

<0.001^b

 Yes

95 (86.4)

89 (83.2)

60 (58.8)

66 (62.3)

 No

15 (13.6)

18 (16.8)

42 (41.2)

40 (37.7)

Physical activity n (%)

<0.001^b

 Yes

53 (48.2)

27 (25.2)

12 (11.8)

56 (52.8)

 No

57 (51.8)

80 (74.8)

90 (88.2)

50 (47.2)

Personal medical history n (%)

0.060^b

 Asthma

4 (3.6)

6 (5.6)

3 (2.9)

9 (8.5)

 Pneumonia

2 (1.8)

2 (1.8)

2 (2.0)

0 (0.0)

 Hypertension

0 (0.0)

0 (0.0)

0 (0.0)

2 (1.9)

 Others

1 (1.0)

1 (1.0)

4 (3.9)

7 (6.6)

 Never

103 (93.6)

98 (91.6)

93 (91.2)

88 (83)

 FEV₁ Mean (SD)

2.7 9 (0.4)

2.64 (0.5)

2.71 (0.5)

2.80 (0.6)

0.14^a

 FEV₁% of predicted Mean (SD)

75.8 (12.1)

76 (14)

76.7 (14.8)

80.6 (11.3)

0.076^a

 FVC Mean (SD)

3.02 (0.71)

3.34 (0.53)

3.44 (0.78)

2.85 (0.48)

<0.001^a

 FVC% of predicted Mean (SD)

75.2 (13.1)

81.6 (10.6)

82.8 (11.8)

80.6 (11.3)

<0.001^a

 FEV₁/FVC Mean (SD)

78.5 (11.8)

77.6 (13.3)

79.4 (13)

79.88 (8.3)

0.51^a