TABLE 3.

Results of proportional hazards regression analyses of five symptom groups on incident COPD events during follow up of subjects with normal and subjects with reduced forced expiratory volume in 1 s (FEV₁)/vital capacity (VC).

	Nonobstructive #		Obstructive ¶
	Wald's Chi-squared +	p-value	Wald's Chi-squared +	p-value
Subjects n	544		71
Nonproductive cough §	3.68	0.054	1.02	0.31
N2-slope quintilesƒ	10.90	0.001	6.33	<0.05
Attained age##	0.13	0.72	0.91	0.34
Smoking habit score¶¶	0.29	0.59	0.42	0.52
Productive cough §	3.86	<0.05	2.51	0.11
N2-slope quintilesƒ	11.71	0.0006	7.26	0.0071
Attained age##	0.13	0.72	0.89	0.35
Smoking habit score¶¶	0.38	0.54	0.51	0.48
Wheezing §	9.65	0.0019	5.98	0.0145
N2-slope quintilesƒ	11.86	0.0006	5.91	0.0150
Attained age##	0.002	0.97	1.28	0.26
Smoking habit score¶¶	0.41	0.52	0.17	0.68
Dyspnoea §	14.51	0.0001	5.94	0.0148
N2-slope quintilesƒ	10.28	0.0013	7.58	0.0059
Attained age##	0.003	0.96	0.08	0.78
Smoking habit score¶¶	0.62	0.43	0.30	0.58
Total symptom score ++	14.82	<0.0001	6.58	0.0103
N2-slope quintilesƒ	10.26	0.0014	6.35	0.0117
Attained age##	0.06	0.81	1.66	0.20
Smoking habit score¶¶	0.06	0.81	0.34	0.56

p<0.05 was considered significant. ^#: FEV₁/VC ≥lower limit of normal (LLN) according to Hedenström et al. [16]; ^¶: FEV₁/VC <LLN according to Hedenström et al. [16]; ⁺: expresses impact of exposures on outcome; ^§: represented by the sum of the questions involved; ^ƒ: alveolar slope of the single-breath nitrogen test in percentage of predicted normal according to Sixt et al. [17] in quintiles; ^##: 50- or 60-year-old men in 1973; ^¶¶: comprises five categories (never-smoker, ex-smoker, currently smoking 1–14 g·day⁻¹, 15–24 g·day⁻¹ and >24 g·day⁻¹); ⁺⁺: sum of yes-responses from all 12 symptoms.