Decline in FEV₁ in Relation to Incident Chronic Obstructive Pulmonary Disease in a Cohort with Respiratory Symptoms

Figures & data

Table 1 Basic characteristics of study population at entry in 1986 (N = number of subjects, M = men, W = women), including lung function (FEV₁ percent predicted, pp) by gender, age group, smoking categories, and chronic productive cough

Variable	Category	N (M/W)	FEV1 pp (M)	FEV1 pp (W)	p-value	All	p-value
Age group	Born 1919–1920	156/145	90.53 (±18.58)	89.17 (±21.05)	0.875	90.35 (±19.77)
	Born 1934–1935	230/202	92.39 (±16.12)	90.20 (±17.27)	0.174	91.37 (±16.69)	0.466^= < 0.001
	Born 1949–1950	189/187	94.98 (±13.48)	95.32 (±11.11)	0.792	95.15 (±12.34)	< 0.001^=
Smoking	Non-smoker	126/252	95.83 (±15.40)	94.09 (±16.55)	0.326	94.67 (±16.18)
	Persistent ex-smoker	198/44	92.39 (±17.48)	92.65 (±16.28)	0.903	92.47 (±17.07)	0.089^§
	Quitter	80/55	94.19 (±16.16)	88.75 (±18.55)	0.073	91.00 (±15.08)	0.103^§
	Restart smoking	9/13	89.89 (±15.88)	95.85 (±8.04)	0.259	93.41 (±11.92)	0.719^§
	Persistent smoker	151/116	89.81 (±14.43)	88.06 (±16.88)	0.363	89.05 (±15.54)	< 0.001^§
Chron prod cough	No	317/327	94.91 (±14.76)	93.98 (±15.55)	0.442	94.44 (±15.16)
	Yes	258/207	90.07 (±17.20)	88.83 (±18.13)	0.450	89.52 (±17.66)	< 0.001^‖

*p-value comparing gender.

⁼ p-value (t-test) comparing means between age group born 1919–1920 and 1934–1935, 1919–1920 and 1949–1950.

^‡ p-value (t-test) comparing means between age group born 1934–1935 and 1949–1950.

^§ p-value (t-test) comparing means between non-smokers and the other five smoking categories, one at a time.

^‖p-value (t-test) comparing means between chronic productive cough positive or negative answer.

Figure 1 Smoking categories, by age group (year of birth) and gender.

Table 2 Lung function in 1986 and 1996, by gender

Categories	Year	Variable	Men	Women	p-value^=	All
All	1986	FEV1	3.47 (±0.79)	2.47 (±0.60)	< 0.001	2.99 (±0.87)
	1996	FEV1	3.08 (±0.83)	2.20 (±0.59)	< 0.001	2.66 (±0.85)
		p-value^‡	< 0.001	< 0.001		< 0.001
	1986	FEV1 pp	92.74 (±16.11)	91.99 (±16.77)	0.446	92.38 (±16.43)
	1996	FEV1 pp	91.21 (±18.96)	91.87 (±18.11)	0.557	91.53 (±18.55)
		p-value^‡	0.001	0.777		0.006
	1986	FEV1/FVC	0.77 (±0.09)	0.78 (±0.09)	< 0.001	0.77 (±0.08)
	1996	FEV1/FVC	0.74 (±0.10)	0.76 (±0.09)	0.001	0.75 (±0.10)
		p-value^‡	< 0.001	< 0.001		< 0.001

*mean ± standard deviation.

⁼comparing gender.

^‡comparing 1986 and 1996.

Table 3 Gender-specific mean decline in FEV₁ (ml/year ± SD) by smoking categories, age group, and chronic productive cough

Variable	Category	Men	Women	p-value	All	p-value
Gender		39 (±34)	28 (±23)	< 0.001	33 (±30)
Smoking	Non-smoker	36 (±40)	25 (±21)	< 0.001	28 (±29)
	Persistent ex smoker	35 (±32)	27 (±22)	0.018	32 (±30)	0.081^=
	Quitter	43 (±34)	24 (±21)	< 0.001	35 (±31)	0.020^=
	Re-starter	44 (±35)	43 (±38)	0.911	43 (±36)	0.024^=
	Persistent smoker	43 (±32)	35 (±22)	0.034	39 (±28)	< 0.001^=
Age group, born	1919–20	41 (±39)	26 (±22)	< 0.001	34 (± 32)
	1934–35	43 (±35)	29 (±23)	< 0.001	36 (±31)	0.264^‡
	1949–50	33 (±30)	28 (±23)	0.052	30 (±26)	0.136^‡, 0.003^§
Chron productive cough	Yes	40 (±37)	30 (±24)	< 0.001	36 (±32)
	No	38 (±33)	26 (±21)	< 0.001	32 (±28)	0.044^‖

*p-value (t-test) comparing means between men and women.

⁼ p-value (t-test) comparing means between non-smokers and the other five smoking categories, one at a time.

^‡ p-value (t-test) comparing means between age group born 1919–1920 and 1934–1935, 1919–1920 and 1949–1950.

^§ p-value (t-test) comparing means between age group born 1934–1935 and 1949–1950.

^‖ p-value (t-test) comparing means between chronic productive cough positive or negative answer.

Table 4 Gender-specific decline in FEV₁ estimated as changes from 1986 to 1996 in percent of predicted normal value by smoking habits, age group and chronic productive cough (FEV₁ % predicted 1996-FEV₁ % predicted 1986; negative result is consistent with decline)

Variable	Category	Men	Women	p-value	All	p-value
Gender		−1.53 (±10.7)	−0.12 (±9.8)	0.023	−0.85 (±10.3)
Smoking	Non-smoker	−0.70 (±11.62)	1.38 (±9.77)	0.068	0.69 (±10.5)
	Persistent ex-smoker	−0.16 (±10.37)	0.37 (±9.10)	0.672	0.01 (±9.96)	0.398^=
	Quitter	−3.00 (±11.83)	1.25 (±8.24)	0.023	−1.27 (±10.69)	0.064^=
	Re-starter	−3.11 (±10.47)	−6.31 (±13.12)	0.550	−5.00 (±11.95)	0.014^=
	Persistent smoker	−2.95 (±9.63)	−3.75 (±9.58)	0.499	−3.30 (±9.60)	< 0.001^=
Age group, born	1919–1920	−2.16 (±13.59)	0.31 (±11.06)	0.086	−0.97 (±12.47)
	1934–1935	−2.80 (±10.69)	−0.80 (±10.42)	0.050	−1.86 (±10.60)	0.297^‡
	1949–1950	0.55 (±7.37)	0.28 (±7.83)	0.734	0.41 (±7.59)	0.076^‡ 0.001^§
Chron productive cough	Yes	−2.50 (±11.74)	−1.38 (±10.59)	0.287	−2.00 (±11.25)
	No	−0.74 (±9.80)	0.68 (±9.16)	0.059	−0.02 (±9.50)	0.002^‖

*p-value (t-test) comparing means between men and women.

⁼ p-value (t-test) comparing means between non-smokers and the other five smoking categories, one at a time.

^‡ p-value (t-test) comparing means between age group born 1919–1920 and 1934–1935, 1919–1920 and 1949–1950.

^§ p-value (t-test) comparing means between age group born 1934–1935 and 1949–1950.

^‖ p-value (t-test) comparing means between chronic productive cough positive or negative answer.

Figure 2 Decline in FEV₁ during 10 years in men and women by smoking habits (never = never smoker, ex = ex-smoker, smoker = current smoker) and age at start of the observation period adjusted for family history of OLD and socio-economic class in a multiple linear regression model.

Table 5 The influence of age and smoking categories on the decline in FEV₁ during the observation period by logistic linear regression. Other independent variables in the model were family history of OLD, socioeconomic class and chronic bronchitis at start of the observation period

Variable	Men			Women
	Constant	SE	p-value	Constant	SE	p-value
Constant	0.467	0.041	< 0.001	0.267	0.027	< 0.001
Age^=	0.049	0.019	0.013	0.009	0.013	0.390
Re-starters^‡	0.080	0.116	0.492	0.182	0.063	0.004
Persistent smokers^‡	0.063	0.033	0.055	0.106	0.024	< 0.001

*express the 10 year decline of FEV₁ in liters.

⁼effect of 10 years ageing.

^‡effect compared with effect of non-and ex-smoker.

Table A1 Decline in FEV₁ (litre) during the 10-year period, by age at start of follow-up and smoking category

	Men			Women
Age at start	Re-starter*	P smoker^=	Reference^‡	Re-starter	P smoker^=	Reference^‡
35	0.402	0.386	0.323	0.421	0.346	0.240
40	0.418	0.401	0.338	0.424	0.348	0.243
45	0.433	0.417	0.354	0.427	0.351	0.246
50	0.449	0.433	0.369	0.430	0.354	0.248
55	0.465	0.448	0.385	0.433	0.357	0.251
60	0.480	0.464	0.400	0.436	0.360	0.254
65	0.496	0.479	0.416	0.439	0.363	0.257

*Re-start of smoking.

⁼Persistent smoking.

^‡Reference group including non-smoking, ex-smoking and intermittent smoking.