Table 3 Pooled estimates of effects of risk factors on Global Initiative for Chronic Obstructive Lung Disease stage I or higher chronic obstructive pulmonary disease (COPD)# adjusted for all risk factors in the regression model, including pack-years of smoking
OR (95% CI)p-valueI2 %p-value for heterogeneity
Female0.75 (0.64–0.89)0.001300.11
Age (per 10-yr difference)2.14 (1.98–2.31)<0.001410.042
BMI kg·m−2
 25–300.64 (0.51–0.79)<0.001580.002
 >300.60 (0.47–0.76)<0.001530.006
Education0.81 (0.74–0.89)<0.00100.62
Hospitalisation for breathing problems before age 10 yrs2.11 (1.29–3.44)0.003610.001
Current smoking1.34 (1.12–1.61)0.002300.11
Passive smoking+1.22 (1.06–1.41)0.00670.38
Doctor ever-diagnosed tuberculosis1.72 (1.19–2.48)0.004560.003
Family history of COPD§1.38 (1.17–1.63)<0.00100.75
Years working in dusty jobs per 10-yr difference1.08 (1.02–1.13)0.00310.44
Regular exposure to dust in present job0.85 (0.66–1.11)0.23430.032
Regular exposure to fumes in present job1.00 (0.79–1.26)0.9700.62
Years exposed to biomass fires per 10-yr differenceƒ
 For heating1.03 (0.97–1.10)0.3300.52
 For cooking##0.98 (0.70–1.37)0.9140.41
  • BMI: body mass index. #: stage I or higher COPD defined as forced expiratory volume in 1 s/forced vital capacity ratio <0.7. : effect per group, assuming a linear effect over the four groups of highest level of education, as follows: none; primary (primary or middle school); secondary (secondary school); tertiary (technical/vocational college or university). +: somebody else smoking in the subject's home in the last 2 weeks. §: doctor ever-diagnosed mother, father, sister or brother with emphysema, chronic bronchitis or COPD. ƒ: fires burning coal, coke, peat, wood, crop residue or dung. ##: years of equivalent continuous exposure are calculated by multiplying number of years over which subject was exposed by number of hours of exposure per day divided by 24.