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Table 1 Characteristics of the study participants

From: Air pollution exposure and lung function in highly exposed subjects in Beijing, China: a repeated-measure study

  Office workers Truck drivers p-valuea
  (n = 60) (n = 60)  
Sex, n (%)   
Male 40 (66.7) 40 (66.7)  
Female 20 (33.3) 20 (33.3) 1.00
Smoking, n (%)   
Never smoker 35 (58.3) 34 (56.7)  
Former 2 (3.3) 2 (3.3)  
Current 23 (38.3) 24 (40.0) 1.00
Age [years], mean (SD) 30.3 ± 8.0 33.5 ± 5.7 0.01
BMI [kg/m 2 ], mean (SD) 22.8 ± 3.4 24.3 ± 3.2 0.01
Time spent commuting to work, mean (SD) 6.9 ± 9.0 12.4 ± 15.2 <0.001
Cigarettes smoked during examination time, mean (SD) b 0.5 ± 1.7 2.3 ± 4.2 0.003
Work hours per week, mean ± SD 50.6 ± 11.0 67.3 ± 14.0 <0.001
Study day of the week, n (%)   
Monday 16 (13.3) 19 (15.8)  
Tuesday 18 (15.0) 13 (10.8)  
Wednesday 14 (11.7) 15 (12.5)  
Thursday 15 (12.5) 20 (16.7)  
Friday 17 (14.2) 19 (15.8)  
Saturday 18 (15.0) 16 (13.3)  
Sunday 22 (18.3) 18 (15.0) 0.8c
Average temperature on two study days, mean (SD) 25.4 ± 2.5 25.3 ± 2.5 0.96c
Average dew point on two study days, mean (SD) 20.6 ± 2.1 20.6 ± 2.1 0.93c
  1. aP-values were calculated using Student’s t-test and Fisher’s exact test for continuous and categorical variables, respectively.
  2. bOnly current or former smokers.
  3. cCumulative of the two study days. Based on 240 total observations (120 study days for office workers and 120 study days for truck drivers). P-values were obtained from mixed-effects regression models.