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-value	I² %	p-value for heterogeneity
Female	0.75 (0.64–0.89)	0.001	30	0.11
Age (per 10-yr difference)	2.14 (1.98–2.31)	<0.001	41	0.042
BMI kg·m⁻²
<25	1.00
25–30	0.64 (0.51–0.79)	<0.001	58	0.002
>30	0.60 (0.47–0.76)	<0.001	53	0.006
Education^¶	0.81 (0.74–0.89)	<0.001	0	0.62
Hospitalisation for breathing problems before age 10 yrs	2.11 (1.29–3.44)	0.003	61	0.001
Current smoking	1.34 (1.12–1.61)	0.002	30	0.11
Passive smoking⁺	1.22 (1.06–1.41)	0.006	7	0.38
Doctor ever-diagnosed tuberculosis	1.72 (1.19–2.48)	0.004	56	0.003
Family history of COPD^§	1.38 (1.17–1.63)	<0.001	0	0.75
Years working in dusty jobs per 10-yr difference	1.08 (1.02–1.13)	0.003	1	0.44
Regular exposure to dust in present job	0.85 (0.66–1.11)	0.23	43	0.032
Regular exposure to fumes in present job	1.00 (0.79–1.26)	0.97	0	0.62
Years exposed to biomass fires per 10-yr difference^ƒ
For heating	1.03 (0.97–1.10)	0.33	0	0.52
For cooking^##	0.98 (0.70–1.37)	0.91	4	0.41

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.