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

Table 1 Characteristics of the study participants

	Office workers	Truck drivers	p-value^a
	(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)	0.8^c
Average temperature on two study days, mean (SD)	25.4 ± 2.5	25.3 ± 2.5	0.96^c
Average dew point on two study days, mean (SD)	20.6 ± 2.1	20.6 ± 2.1	0.93^c

^aP-values were calculated using Student’s t-test and Fisher’s exact test for continuous and categorical variables, respectively.
^bOnly current or former smokers.
^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.

ISSN: 1743-8977