Rate of progression of CT-quantified emphysema in male current and ex-smokers: a follow-up study

Respiratory Research

Table 3 Effect estimates of listed parameters on the increase of the % lung volume <-950 HU values

Parameter	Effect size	p-value.	95% CI of effect size
Parameter	Effect size	p-value.	Lower bound	Upper bound
center
UMCU	1.01	0.619	0.97	1.05
UMCG (reference)
smoking group
current smoker	0.60	<0.001	0.56	0.64
quitted <1 year	0.91	0.083	0.82	1.01
quitted ≥1 – <5 years	0.99	0.868	0.92	1.07
quitted ≥5years (reference)
baseline GOLD stage
normal	0.18	0.002	0.06	0.54
stage I	0.28	0.022	0.09	0.83
stage II	0.31	0.040	0.10	0.95
stage III	0.47	0.183	0.15	1.43
stage IV (reference)
height (cm)	1.01	<0.001	1.07	1.01
Presence of respiratory symptoms
cough	0.96	0.647	0.93	1.05
wheezing	1.01	0.881	0.94	1.07
dyspnea	0.99	0.773	0.94	1.05
mucus	1.02	0.724	0.96	1.09
age at start study (years)	1.02	<0.001	1.01	1.02
packyears	0.99	<0.001	0.97	0.99
observation time	1.07	<0.001	1.06	1.09
*observation time smoking group**
current smoker	1.05	<0.001	1.03	1.07
quitted <1 year	0.99	0.799	0.97	1.02
quitted ≥1 – <5 years	0.99	0.234	0.97	1.01
quitted ≥5years (reference)

The column headed with ‘effect size’ again contains the change in % lung volume <-950 HU due to a unit change in the parameter or due to membership of another class. For instance, for each year a subject is older at the start of the study, the % lung volume <-950 HU increases with a factor of 1.02. For class comparisons the changes are versus the reference group: so a subject with an FEV1/FVC >70% (no COPD) has a 0.18 times lower lung volume <-950 HU compared to the reference GOLD class 4 (the p-value for this comparison is 0.002). The parameter observation time denotes the annual change in % lung volume <-950 HU being times 1.07 higher per year.

ISSN: 1465-993X