Impact of Education on COPD Severity and All-Cause Mortality in Lifetime Never-Smokers and Longtime Ex-Smokers: Results of the COSYCONET Cohort

Figures & data

Figure 1 Consort diagram of the study population.

Table 1 Baseline Characteristics of the Study Sample Stratified by Smoking Status

n		Never-Smoker	Ex-Smoker	p-value^a
		150	616
Male		70 (46.7)	432 (70.1)	<0.0001
Age, yrs		68.5 ± 8.4	68.3 ± 7.7	0.7268
BMI category^b	Underweight	4 (2.7)	10 (1.6)	0.0531
	Normal	65 (43.6)	201 (32.7)
	Overweight	54 (36.2)	265 (43.1)
	Obese	26 (17.5)	139 (22.6)
Education^c	Basic education	77 (51.3)	349 (56.7)	0.4924
	Secondary education	41 (27.3)	153 (24.8)
	Higher education	32 (21.3)	114 (18.5)
Pulmonary function	FEV1% pred	55.2 ± 18.4	53.1 ± 19.1	0.2337
	FVC % pred	76.8 ± 19.7	78.8 ± 19.3	0.2632
	FEV1/FVC (L)	54.9 ± 10.2	51.1 ± 11.1	0.0001
	TLCO % pred	65.2 ± 25.4	57.4 ± 22.5	0.0003
	KCO % pred	79.5 ± 29.0	67.1 ± 22.6	<0.0001
	ITGV % pred	140.8 ± 31.9	146.0 ± 37.6	0.1208
	RV % pred	160.1 ± 45.4	167.2 ± 53.0	0.1423
	RV/TLC	0.55 ± 0.10	0.55 ± 0.11	0.6735
	VA % pred	82.8 ± 16.8	84.4 ± 15.2	0.2719
	TLC % pred	123.5 ± 35.0	115.9 ± 31.2	0.0095
GOLD group (mMRC)	A	60 (41.1)	232 (37.9)	0.8571
	B	36 (24.7)	169 (27.6)
	C	20 (13.7)	80 (13.1)
	D	30 (20.6)	131 (21.4)
Severe exacerbation history	Proportion Yes	24 (16.0)	116 (18.9)	0.4164
	Mean annual rate	1.6 ± 0.7	1.4 ± 0.8	0.3806
Years since COPD diagnosis		12.3 ± 9.8	10.7 ± 7.6	0.0278
AATD		34 (22.7)	60 (9.7)	<0.0001
Symptoms and Quality of life	mMRC	1.5 ± 0.9	1.6 ± 0.9	0.1974
	SGRQ	42.1 ± 18.9	43.8 ± 19.9	0.3238
	activity	55.8 ± 24.5	60.3 ± 25.7	0.0555
	symptoms	54.6 ± 21.9	54.4 ± 21.1	0.9192
	impacts	29.5 ± 20.1	30.5 ± 20.6	0.6065
	CAT	17.5 ± 7.2	18.0 ± 7.2	0.4900
	EQ-VAS	56.7 ± 19.3	55.8 ± 19.6	0.6219
	EQ-5D utility	0.83 ± 0.19	0.82 ± 0.19	0.5629
PHQ-9		5.66 ± 3.99	5.81 ± 4.36	0.7002
TUG		6.76 ± 2.01	7.13 ± 2.59	0.1034
IPAQ		4270.8 ± 4177.8	4373.9 ± 5947.0	0.8441
6MWD		434.3 ± 109.2	405.3 ± 108.5	0.0038
ABI		1.25 ± 0.12	1.19 ± 0.14	<0.0001

Notes: Data are presented as n (%) or mean ± standard deviation. ^a p-value based on Chi²-test (categorical variables) and based on ANOVA (continuous variables). ^b Normal weight (18.5 ≤ BMI <25), overweight (25 ≤ BMI < 30), obese (BMI ≥ 30), and underweight (BMI < 18.5). ^c Basic education (≤9 school years), secondary education (10–11 school years), and higher education (>11 school years). Significant differences between groups are marked in bold (p<0.05).

Table 2 Mean Household Net Income per Month  in Euro by Level of Education

	Mean ± SD	p-value^a
Basic education (≤9 years)	1153 ± 561	<0.0001
Secondary education (10–11 years)	1360 ± 560
Higher education (>11 years)	1684 ± 674

Note: ^a p-value based on ANOVA.

Table 3 Mean Values of Parameters by Smoking Status and Education

	Basic Education (≤9 Years)		Secondary Education (10–11 Years)		Higher Education (>11 Years)		Main Effects		Interaction
	Never-Smoker	Ex-Smoker	Never-Smoker	Ex-Smoker	Never-Smoker	Ex-Smoker	Education	Smoking	Education* Smoking
n	77	349	41	153	32	114	p-value
Lung function parameters
FEV1% pred	49.3	48.7	52.3	51.2	61.3	53.0	0.0012	0.0754	0.1958
FVC % pred	70.7	74.3	74.8	77.6	80.0	78.1	0.0118	0.4347	0.4773
FEV1/FVC (L)	52.9	49.6	53.4	49.9	57.8	51.3	0.0275	<0.0001	0.4313
TLCO % pred	62.6	51.7	62.3	53.4	64.6	56.9	0.4229	<0.0001	0.8178
KCO % pred	79.5	62.4	77.7	65.2	77.6	69.0	0.7838	<0.0001	0.3492
RV/TLC	0.58	0.58	0.57	0.56	0.53	0.56	0.0096	0.3502	0.4299
ITGV % pred	150.8	156.4	144.9	159.2	140.0	152.6	0.2110	0.0021	0.4552
RV % pred	173.3	178.9	165.7	181.4	156.8	172.5	0.1540	0.0140	0.5465
VA % pred	84.8	82.9	77.7	83.7	82.7	81.3	0.1838	0.5704	0.0633
TLC % pred	122.5	123.2	125.2	123.5	113.5	118.4	0.0490	0.6394	0.6554
Symptoms, health-related quality of life, exercise capacity and functioning
SGRQ	44.5	47.3	43.0	43.2	37.8	39.5	0.0081	0.4270	0.8275
Activity	60.0	65.5	58.8	60.8	44.7	55.6	0.0001	0.0146	0.4076
Symptoms	55.4	55.3	51.9	54.6	55.8	49.7	0.4939	0.5973	0.3025
Impacts	31.5	33.8	30.3	29.0	27.5	26.4	0.0571	0.9968	0.6647
CAT	18.7	19.4	18.0	17.9	16.4	17.6	0.0518	0.4059	0.7418
EQ-VAS	53.9	51.4	56.1	54.0	57.7	59.3	0.0422	0.6068	0.6610
EQ-5D utility	0.78	0.79	0.86	0.78	0.81	0.84	0.1229	0.3552	0.1140
mMRC	1.59	1.76	1.65	1.67	1.42	1.50	0.1329	0.3290	0.7365
IPAQ	3591.4	3844.7	4111.0	3500.6	3786.3	3857.7	0.9847	0.8698	0.7898
6MWD	424.9	390.0	416.9	403.3	484.7	426.2	0.0004	0.0007	0.2757
Time up and go	6.86	7.21	6.55	6.97	5.99	6.60	0.0422	0.0615	0.9139
PHQ9	6.11	6.96	6.29	6.36	6.79	6.46	0.8553	0.6406	0.4436
ABI	1.26	1.18	1.23	1.20	1.27	1.19	0.8192	<0.0001	0.2178

Notes: Models were adjusted for age, sex, BMI, and time since COPD diagnosis. *marks the interaction between school and smoking. Significant associations are marked in bold (p<0.05).

Figure 2 Mean values of lung function parameters by smoking status and by education. Multiple ANOVA models (A–D) were adjusted for age, sex, body mass index (BMI), years since COPD diagnosis, and smoking status*education. Education was categorized as basic education (≤9 years), secondary education (10–11 years), and higher education (>11 years).

Figure 3 Mean values of health-related quality of life and exercise capacity by smoking status and by education. Multiple ANOVA models (A–C) were adjusted for age, sex, body mass index (BMI), years since COPD diagnosis, and smoking status*education. Education was categorized as basic education (≤9 years), secondary education (10–11 years), and higher education (>11 years).

Table 4 Association Between Comorbidities, Smoking Status, and Education

	Education			Smoking Status
	Basic (≤9 Years)	Secondary (10–11 Years)	Higher (>11 Years)	Ex-Smoker	Never-Smoker
		OR (95% CI)	OR (95% CI)		OR (95% CI)
AATD	ref.	2.01 (1.16–3.47)	1.54 (0.84–2.84)	ref.	2.60 (1.55–4.37)
Diabetes	ref.	0.81 (0.47–1.38)	0.69 (0.38–1.24)	ref.	1.02 (0.57–1.81)
Hypertension	ref.	1.26 (0.87–1.83)	1.08 (0.72–1.61)	ref.	0.89 (0.61–1.31)
Asthma	ref.	1.06 (0.69–1.63)	1.99 (1.28–3.08)	ref.	2.34 (1.57–3.49)
KHK	ref.	0.76 (0.47–1.23)	0.72 (0.43–1.20)	ref.	0.75 (0.43–1.30)
Bronchiectasis	ref.	0.85 (0.37–1.96)	1.22 (0.54–2.74)	ref.	5.00 (2.55–9.81)
Hyperuricemia	ref.	0.88 (0.56–1.40)	0.76 (0.46–1.26)	ref.	0.89 (0.53–1.48)
HLP	ref.	0.92 (0.65–1.31)	0.75 (0.51–1.10)	ref.	0.91 (0.63–1.32)
Osteoporosis	ref.	0.69 (0.43–1.09)	0.63 (0.37–1.08)	ref.	1.48 (0.95–2.31)
GI	ref.	0.83 (0.59–1.18)	0.74 (0.50–1.08)	ref.	0.78 (0.54–1.13)

Notes: Logistic regression models were adjusted for age, sex, and BMI (estimates not shown). Significant associations are marked in bold (p<0.05).