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Table 1 Characteristics of the study participants

From: Inhalable particulate matter and mitochondrial DNA copy number in highly exposed individuals in Beijing, China: a repeated-measure study

 

Office workers

Truck drivers

p-value a

 

(n=60)

(n=60)

 

Age [years], mean ± SD

30.27 ± 7.96

33.53 ± 5.65

0.01

Sex, n (%)

   

      Male

40 (66.67)

40 (66.67)

 

      Female

20 (33.33)

20 (33.33)

1.00

BMI [kg/m 2 ], mean ± SD

22.76 ± 3.38

24.27 ± 3.21

0.01

Smoking, n (%)

   

      Never smoker

35 (58.33)

34 (56.67)

 

      Former

2 (3.33)

2 (3.33)

 

      Current

23 (38.33)

24 (40)

1.00

Pack-years of smoking, mean ± SD b

1.2 ± 2.7

5.1 ± 9.3

0.003

Work hours per week, mean ± SD

50.6 ± 11.0

67.3 ± 14.0

<0.001

Day of the week on the two study days, n (%)

   

      Monday

16 (13.33)

19 (15.83)

 

      Tuesday

18 (15)

13 (10.83)

 

      Wednesday

14 (11.67)

15 (12.5)

 

      Thursday

15 (12.5)

20 (16.67)

 

      Friday

17 (14.17)

19 (15.83)

 

      Saturday

18 (15)

16 (13.33)

 

      Sunday

22 (18.33)

18 (15)

0.88c

Average temperature on the two study days, mean ± SD

25.36 ± 2.51

25.34 ± 2.51

0.96c

Average dew point on the two study days, mean ± SD

20.63 ± 2.06

20.61 ± 2.13

0.93c

  1. a P-values were calculated using Student’s t-test and Fisher’s exact test for continuous and categorical variables, respectively.
  2. b Only current or former smokers.
  3. c Cumulative over 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.