Table 1

Characteristics of the study participants by dense traffic exposure category (distance to the nearest road with more than 10 000 vehicles per day).

Dense traffic exposure
Low (>500 m)Medium (75–500 m)High (<75 m)
All participants (n=5441)n=2410n=2668n=363
Mean (SD)Mean (SD)Mean (SD)
Age, years51.8 (11.0)51.5 (11.6)50.1 (12.4)
Body mass index (BMI)26.2 (4.0)26.0 (4.1)26.2 (4.5)
Lung function
 FEV1 (% predicted)96.9 (13.8)96.2 (13.5)96.0 (13.6)
 FVC (% predicted)98.5 (12.5)98.2 (12.2)97.7 (12.9)
Per centPer centPer cent
Sex (% women)52.254.454.5
Smoking history
 Never smoked (n=2509)47.245.643.0
 Former smoker (n=2023)37.037.536.4
 Current smoker (n=909)15.916.920.7
Highest formal education
 Primary education (n=664)
 Upper primary education (n=184)
 Vocational school (n=404)
 High school (n=1254)24.322.319.8
 University (n=2048)34.139.550.4
 Other education (n=887)17.115.515.7
Obstructive pulmonary disease* (n=533)9.010.310.7
  • *Reported current asthma or fulfils criteria for chronic obstructive pulmonary disease (COPD) in regular spirometry test without reversibility testing.

  • BMI, body mass index; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.