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Table 3 Individual and joint association of smoking and PM2.5 with COPD among participants in this study

From: Joint association of cigarette smoking and PM2.5 with COPD among urban and rural adults in regional China

Exposure variables

Prevalence of COPD among participants,% (n/N)

OR (95%CI)

Smoking exposure

Annual mean PM2.5 exposure

Model 1a

Model 2b

Non-smokers

N/A

6.4 (132/2073)

1

 

1

 

Smokers

N/A

20.6 (275/1334)

2.64 (1.89, 3.68)

 

2.46 (1.76, 3.43)

 

N/A

< 75 μg/m3

10.9 (/2,462,267)

1

 

1

 

N/A

≥ 75 μg/m3

14.1 (161/1140)

1.26 (1.01, 1.58)

 

1.29 (1.02, 1.64)

 

Non-smokers

< 75 μg/m3

6.3 (90/1420)

1

 

1

 

Non-smokers

≥ 75 μg/m3

6.4 (42/653)

1.00 (0.67, 1.46)

 

1.10 (0.74, 1.64)

 

Smokers

< 75 μg/m3

18.4 (156/847)

2.29 (1.56, 3.37)

1

2.22 (1.51, 3.27)

1

Smokers

≥ 75 μg/m3

24.4 (119/487)

2.96 (2.04, 4.31)

1.43 (1.09, 1.88) c

3.14 (2.15, 4.59)

1.36 (1.01, 1.83)c

  1. Smoking exposure: −, Non-smoker; + , smoker
  2. Annual mean PM2.5 exposure: −, < 75 μg/m3; + , ≥ 75 μg/m3
  3. aModel 1 was a univariate analysis with smoking exposure or annual mean PM2.5 as main effects and study sites as random effects
  4. bModel 2 was a multivariate analysis with adjustment for age, gender, residence, education, occupation, biomass use, parental history of respiratory diseases,body weight status, annual mean PM2.5 exposure/cigarette smoking, in addition to Model 1
  5. cThe OR predicted the likelihood for smokers who exposed to PM2.5 ≥ 75 μg/m3 to experience COPD compared to their counterparts who exposed to PM2.5 < 75 μg/m3 in this study