Table 1 Baseline characteristics

 40–49

1,025 (25.0)

21 (17.1)

<0.001***

 50–59

1,098 (26.8)

15 (12.2)

 60–69

1,020 (24.9)

39 (31.7)

 ≥70

951 (23.2)

48 (39.0)

 Male

1,731 (42.3)

61 (49.6)

0.116

 Female

2,363 (57.7)

62 (50.4)

 Underweight (<18.5)

1,508 (36.8)

48 (39.0)

0.118

 Normal (18.5–22.9)

113 (2.8)

6 (4.9)

 Overweight (23–24.9)

999 (24.4)

37 (30.1)

 Obese I (25.0–29.9)

1,266 (30.9)

26 (21.1)

 Obese II (≥30)

207 (5.1)

6 (4.9)

 Never-smoker

2,493 (61.0)

64 (52.0)

 Ever-smoker (current or ex-smoker)

1,592 (39.0)

59 (48.0)

0.049*

 Current smoker

592/4085 (14.5)

37/123 (30.1)

<0.001***

 Normal

1,312 (32.0)

30 (24.4)

0.191

 Pre-hypertension

1,067 (26.1)

37 (30.1)

 Hypertension

1,715 (41.9)

56 (45.5)

 Normal

1,272 (32.6)

28 (24.6)

<0.001***

 Pre-diabetes

1,911 (48.9)

62 (54.4)

 Diabetes mellitus

724 (18.5)

24 (21.1)

 No asthma history

3984 (97.3)

109 (88.6)

<0.001***

 Asthma history

110 (2.7)

14 (11.4)

 No Allergic rhinitis history

3618 (88.4)

109 (88.6)

1.000

 Allergic rhinitis history

476 (11.6)

14 (11.4)

 No sinusitis history

3871 (94.6)

115 (93.5)

0.547

 Sinusitis history

223 (5.4)

8 (6.5)

 FVC (L)

3.19 (2.65–3.83)

2.86 (2.42–3.66)

0.003**

 FVC (% of predicted)

87.5 (79.6–95.6)

84.0 (75.9–92.0)

0.001**

 FEV₁ (L)

2.47 (2.06–2.95)

2.03 (1.64–2.63)

<0.001***

 FEV₁ (% of predicted)

87.7 (79.7–96.0)

80.6 (72.3–90.0)

<0.001***

  ≥80

2,656 (74.4)

55 (53.4)

<0.001***

  ≥50–<80

887 (24.8)

42 (40.8)

  ≥30–<50

24 (0.7)

4 (3.9)

  <30

4 (0.1)

2(1.9)

 High

1,117 (27.4)

20 (16.4)

<0.001***

 Middle–high

989 (24.2)

19 (15.6)

 Middle–low

1,058 (25.9)

36 (29.5)

 Low

916 (22.5)

47 (38.5)

 Employed

2,431 (59.4)

53 (43.1)

<0.001***

 Unemployed, inactive

1,662 (40.6)

70 (56.9)

 High (>9years)

2,576 (63.0)

66 (53.7)

0.038*

 Low (≤9 years)

1,515 (37.0)

57 (46.3)