Table 4—

Adjusted odds ratio(OR) of potential risk factors for previous Global Initiative for Chronic Obstructive Lung Disease (GOLD) staging among nonsmoking chronic obstructive pulmonary disease (COPD) subjects

	Stage 0		Stage I		Stage II–IV		p-value^#
	OR (95% CI)	p-value	OR (95% CI)	p-value	OR (95% CI)	p-value	p-value^#
Sex		0.720		0.001		<0.001	<0.001
Male	0.96 (0.76–1.21)		1.82 (1.27–2.62)		2.00 (1.60–2.51)
Female^¶	1		1		1
Age yrs		<0.001		<0.001		<0.001	<0.001
40–49^¶	1		1		1
50–59	1.41 (1.12–1.78)		2.23 (1.26–3.96)		2.04 (1.41–2.95)
60–69	1.74 (1.35–2.23)		4.35 (2.48–7.60)		4.55 (3.20–6.47)
≥70	2.46 (1.84–3.28)		10.20 (5.72–18.17)		10.34 (7.20–14.85)
Education yrs		0.103		0.424		<0.001	<0.001
0	0.72 (0.51–1.02)		1.18 (0.57–2.43)		2.36 (1.40–4.00)
1–9	0.78 (0.57–1.06)		0.96 (0.48–1.91)		1.66 (1.00–2.77)
≥10^¶	1		1		1
BMI kg·m⁻²		0.228		0.169		<0.001	<0.001
<18.5	0.99 (0.60–1.63)		1.37 (0.61–3.12)		3.16 (2.06–4.86)
18.5–23.9	0.83 (0.64–1.07)		1.28 (0.78–2.12)		1.27 (0.92–1.74)
24.0–27.9	0.92 (0.71–1.18)		1.01 (0.60–1.69)		0.85 (0.61–1.19)
≥28.0^¶	1		1		1
Passive smoking⁺		0.178		0.044		0.039	0.479
No^¶	1		1		1
Yes	1.16 (0.94–1.42)		1.51 (1.01–2.26)		1.29 (1.01–1.65)
Respiratory disease in family		<0.001		0.004		<0.001	0.638
None^¶	1		1		1
1 affected	1.64 (1.33–2.01)		1.98 (1.37–2.87)		2.04 (1.60–2.60)
≥2 affected	2.80 (2.07–3.78)		1.42 (0.72–2.78)		2.55 (1.72–3.76)
Chronic cough in childhood		<0.001		<0.001		<0.001	0.062
Recurrent	4.13 (2.94–5.81)		6.20 (3.26–11.77)		6.11 (3.99–9.34)
Sometimes	2.20 (1.60–3.01)		2.05 (1.05–4.00)		2.76 (1.87–4.08)
Seldom^¶	1		1		1
Exposure to biomass for cooking		0.082		0.772		0.004	0.001
Yes	0.84 (0.69–1.02)		1.05 (0.74–1.49)		1.39 (1.11–1.74)
No^¶	1		1		1
Exposure to biomass for heating		0.108		0.659		0.530	0.395
Yes	2.26 (0.84–6.10)		1.37 (0.34–5.47)		2.83 (0.53–3.44)
No^¶	1		1		1
Exposure to coal for cooking		0.630		0.671		0.231	0.553
Yes	1.05 (0.86–1.29)		1.08 (0.75–1.56)		1.15 (0.91–1.45)
No^¶	1		1		1
Exposure to coal for heating		0.012		0.338		0.015	0.773
Yes	1.46 (1.09–1.97)		1.40 (0.70–2.80)		1.56 (1.09–2.24)
No^¶	1		1		1
Poor ventilation in kitchen		0.004		0.085		0.046	0.698
No^¶	1		1		1
Yes	1.34 (1.10–1.64)		1.36 (0.96–1.93)		1.27 (1.00–1.60)
Occupational exposure to dusts/gases/fumes		0.001		0.137		0.351	0.008
Yes	1.49 (1.17–1.88)		1.40 (0.90–2.18)		0.85 (0.61–1.19)
No^¶	1		1		1

CI: confidence interval; BMI: body mass index. ^#: comparison between OR for stage 0 and stage II–IV; ^¶: reference values; ⁺: defined as exposure to environmental tobacco smoke.