Table 4.

Effect estimates of listed parameters on the longitudinal FEV₁ (milliliters) values

Parameter	Effect size	p-value.	95% CI of effect size
			Lower bound	Upper bound
center
UMCU	-.74.4	<0.001	−103	46
UMCG (reference)
smoking group
current smoker	−101	<0.001	−142	−61
quitted <1 year	−68	0.033	−130	−5
quitted ≥1 – <5 years	−32	0.188	−80	15
quitted ≥5years (reference)
baseline GOLD stage
normal	2346	<0.001	1497	3195
stage I	2035	<0.001	1185	2884
stage II	1187	0.006	337	2037
stage III	346	0.428	−510	1202
stage IV (reference)
height (cm)	044	<0.001	41	46
Presence of respiratory symptoms
cough	−11	0.607	−7	19
wheezing	−106	<0.001	−152	−60
dyspnea	−76	<0.001	−117	−34.7
mucus	12	0.580	−30	54
age at start study (years)	−29	<0.001	−32	−27
packyears	−3.2	<0.001	−4	−2
observation time	−58	<0.001	−66	−48
observation time * smoking group
current smoker	−12	0.029	−22	−1
quitted <1 year	−19	0.019	−35	−3
quitted ≥1 – <5 years	0.8	0.237	−5	20
quitted ≥5years (reference)

The column headed with ‘effect size’ contains the change in FEV1 (millliters) due to a unit change in the parameter or due to membership of another class. So for each year a subject is older at the start of the study the FEV1 decreases with 29 millliters.