Table 2

Characteristics of all study participants

N or mean (SD)COPD (N)Prevalence (%)
Age group, year
Education status
 Under primary school4234811.34
 Primary school155718111.62
 Junior high school20221939.55
 Senior high school1405785.55
 Graduate and above586213.75
Smoking history
Occupational exposure
Biofuel exposure
Family history
History of childhood pneumonia in the hospital
Mother smoking during pregnancy
Mother exposed to second-hand smoking during pregnancy
Kitchen ventilation quality
Environmental tobacco smoking exposure*
Rural and urban distribution
Lung function outcomes
 FEV1, L2.61 (0.7)
 FVC, L3.21 (0.8)
 FEV1%pred, %97.63 (16.2)
 FVC%pred, %99.59 (15.5)
 FEV1/FVC, %81.45 (9.7)
  • Data were collected from all 5993 participants in the seven clusters.

  • *Environmental tobacco smoking exposure was defined using two added scores according to exposure at home and at the workplace.