The contribution of symptoms and comorbidities to the economic impact of COPD: an analysis of the German COSYCONET cohort

Figures & data

Table 1 Characteristics of the study population

Characteristics
N	2,139
Sex
Female	832 (38.9%)
Male	1,307 (61.1%)
Age (years)
Mean	65.4 (±8.2)
>74	258 (12.1%)
65–74	947 (44.3%)
55–64	722 (33.8%)
<55	212 (9.9%)
GOLD spirometric stage
Stage 1 (FEV1% predicted ≥80%)	197 (9.2%)
Stage 2 (50≤ FEV1% predicted <80)	908 (42.5%)
Stage 3 (30≤ FEV1% predicted <50)	810 (37.9%)
Stage 4 (FEV1% predicted <30)	224 (10.5%)
Spirometrya
FEV1 (L), mean	1.55 (±0.6)
FVC (L), mean	2.98 (±1.0)
FEV1GLI Z-score	−2.87 (±1.1)
FVC GLI Z-score	−1.45 (±1.3)
FEV1/FVC GLI Z-score	−2.97 (±1.1)
Smoking status
Current smoker	562 (26.3%)
Former smoker	1,461 (68.3%)
Never smoker	116 (5.4%)
BMI (kg/m^2)
Mean	26.8 (±5.3)
Underweight (BMI <18.5)	76 (3.6%)
Normal weight (18.5≤ BMI <25)	774 (36.2%)
Overweight (25≤ BMI <30)	789 (36.9%)
Obese (BMI ≥30)	499 (23.3%)
Education
Basic school education	1,219 (57.0%)
Secondary school education	557 (26.0%)
Higher school education	363 (17.0%)
Comorbidities
Number of comorbidities, mean	3.7 (±2.5)
Number of comorbidities, median	3 (2–5)
Number of comorbidities ≤3	1,114 (52.1%)
Number of comorbidities >3	1,025 (47.9%)
Symptomsb
Cough (CAT ≥3)	954 (44.9%)
Sputum (CAT ≥3)	993 (46.7%)
Dyspnea (mMRC ≥2)	1,027 (48.5%)
No symptoms	557 (26.0%)

Notes: Data are mean (SD) or n (percentage) or median (interquartile range).

a Post-bronchodilator spirometry

b Thirteen participants had missing CAT scores, and 20 had missing mMRC scale.

Abbreviations: GOLD, Global initiative for Obstructive Lung Disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GLI, Global Lung Function Initiative; BMI, body mass index; CAT, COPD Assessment Test; mMRC, modified Medical Research Council.

Figure 1 Lifetime prevalence (%) of comorbid conditions.

Notes: ^aHeart disease: including cardiac arrhythmia, cardiac insufficiency, narrow coronary vessel, and angina pectoris. ^bPsychiatric disorder: including anxiety, depression, and psychosis. ^cMental deficiency: including weakness of memory, restlessness, disorientation, and confusion. ^dOther lung disease: fibrosis, sarcoidosis, and bronchiectasis.

Table 2 Unadjusted mean annual direct and indirect costs

Cost categories	n	% with costs >0	Unadjusted costs (€, 2012) (SD)
Total direct costs	2,105	99.7	7,263 (9,810)
Outpatient costsa	2,118	95.8	855 (777)
Hospitalization costs	2,115	38.2	3,403 (8,303)
Medication costs	2,139	98.2	2,475 (3,259)
Other direct costsb	2,122	44.0	536 (1,145)
Total indirect costs	779	87.7	23,298 (16,833)

Notes:

a Includes costs for outpatient hospital visits.

b Physiotherapy and in-/outpatient rehabilitation.

Table 3 Results of multivariate regression models for direct and indirect costs

Model variables	Total direct costs		Outpatient costs		Hospitalization costs		Medication costs		Other costsa		Total indirect costsb
	n=2,087		n=2,101		n=2,097		n=2,114		n=2,104		n=773
	Exp(beta)	p-value	Exp(beta)	p-value	Exp(beta)	p-value	Exp(beta)	p-value	Exp(beta)	p-value	Exp(beta)	p-value
Intercept	2,013.78	<0.0001	533.81	<0.0001	720.35	<0.0001	1,070.09	<0.0001	161.76	<0.0001	7,468.58	<0.0001
COPD GOLD stage
Stage 1	Ref		Ref		Ref		Ref		Ref		Ref
Stage 2	1.22	0.006	1.04	0.562	1.45	0.07	1.113	0.094	1.19	0.35	0.94	0.78
Stage 3	1.66	<0.0001	1.05	0.51	2.61	<0.0001	1.32	<0.0001	1.68	0.008	1.18	0.47
Stage 4	2.02	<0.0001	0.98	0.84	3.72	<0.0001	1.31	0.0008	1.74	0.02	1.48	0.15
Sex
Male	Ref		Ref		Ref		Ref		Ref		Ref
Female	0.94	0.17	1.11	0.03	0.78	0.05	1.00	0.93	1.07	0.57	1.03	0.83
Age (years)
<55	Ref		Ref		Ref		Ref		Ref		Ref
55–64	0.96	0.61	0.95	0.53	0.85	0.43	1.04	0.51	0.99	0.97	1.59	0.001
65–74	0.92	0.23	0.93	0.33	0.79	0.28	0.99	0.87	0.74	0.10	–
>74	0.95	0.60	0.96	0.70	0.88	0.62	1.01	0.87	0.59	0.02	–
Smoking status
Never smoker	Ref		Ref		Ref		Ref		Ref		Ref
Former smoker	1.31	0.003	1.04	0.70	1.18	0.54	1.21	0.02	1.75	0.02	1.44	0.22
Current smoker	1.02	0.86	0.94	0.53	0.77	0.37	0.98	0.77	1.17	0.52	1.30	0.40
BMI class
Normal weight	Ref		Ref		Ref		Ref		Ref		Ref
Underweight	1.03	0.79	0.98	0.83	1.12	0.72	0.96	0.66	1.11	0.71	1.03	0.93
Overweight	1.12	0.01	1.02	0.69	1.32	0.04	1.04	0.38	1.06	0.62	0.94	0.64
Obese	1.07	0.23	1.04	0.5043	1.07	0.69	1.07	0.15	0.95	0.71	1.03	0.84
Education
Basic	Ref		Ref		Ref		Ref		Ref		Ref
Secondary	1.06	0.20	0.96	0.38	1.18	0.22	1.00	0.94	1.10	0.43	0.84	0.17
Higher	0.97	0.58	0.93	0.20	0.96	0.81	0.94	0.20	1.09	0.56	0.76	0.10
Comorbidities
Osteoarthritis	1.02	0.55	1.12	0.01	0.96	0.71	1.06	0.09	0.93	0.47	1.13	0.33
Allergy	0.97	0.42	1.08	0.09	0.89	0.35	1.06	0.10	1.13	0.27	0.94	0.64
Varices	1.03	0.49	1.05	0.31	1.03	0.81	1.02	0.58	1.06	0.59	0.95	0.70
Heart diseasec	1.25	<0.0001	1.11	0.04	1.38	0.02	1.18	<0.0001	1.06	0.61	1.29	0.08
Gastritis	0.99	0.87	1.05	0.37	0.95	0.71	1.05	0.23	0.99	0.97	1.08	0.60
Psychiatric disordera	1.36	<0.0001	1.31	<0.0001	1.59	0.002	1.19	<0.0001	1.38	0.01	1.31	0.04
Asthma	1.11	0.05	1.06	0.29	1.03	0.84	1.22	<0.0001	1.28	0.08	0.98	0.87
Gout	1.07	0.22	1.12	0.06	1.07	0.69	1.06	0.22	1.04	0.77	1.12	0.50
Osteoporosis	1.38	<0.0001	1.17	0.01	1.53	0.01	1.24	<0.0001	1.11	0.47	1.26	0.18
Diabetes	1.11	0.09	1.05	0.51	0.95	0.77	1.29	<0.0001	0.85	0.35	1.03	0.87
Gastric ulcer	1.20	0.005	0.96	0.55	1.38	0.08	1.02	0.67	0.87	0.37	1.19	0.34
Cholecystitis/gallstones	1.19	0.006	0.92	0.18	1.48	0.04	0.99	0.81	0.86	0.33	1.02	0.92
Peripheral artery disease	1.14	0.03	1.14	0.05	1.35	0.11	1.05	0.39	1.05	0.76	1.11	0.67
Cancer	1.23	0.001	1.24	0.002	1.09	0.64	1.40	<0.0001	1.14	0.41	1.14	0.59
Sleep apnea	1.21	0.003	1.08	0.30	1.55	0.02	1.05	0.37	1.43	0.03	0.94	0.75
Migraine	1.15	0.03	1.02	0.80	1.35	0.12	1.15	0.02	0.89	0.51	1.14	0.45
Per additional other comorbidity	1.08	0.0006	1.06	0.01	1.14	0.03	1.02	0.35	1.10	0.08	0.96	0.52
Symptoms: high levels
Cough (CAT ≥3)	0.98	0.71	1.01	0.87	0.96	0.81	1.02	0.67	1.09	0.54	0.97	0.83
Sputum (CAT ≥3)	1.08	0.13	1.09	0.12	1.11	0.50	0.95	0.25	1.08	0.54	1.06	0.69
Dyspnea (mMRC ≥2)	1.33	<0.0001	1.11	0.03	1.44	0.005	1.31	<0.0001	1.36	0.006	1.34	0.02

Notes: Estimates with p<0.05 are in bold.

a Psychiatric disorders: including anxiety, depression, and psychosis.

b One hundred and fifty-five participants <65 years were not considered for indirect costs analysis because they stated not to take part in the labor market (eg, housewives/househusband, being unemployed persons), and six had missing information on the number of absence days.

c Heart diseases: including cardiac arrhythmia, cardiac insufficiency, narrow coronary vessel, and angina pectoris.

Abbreviations: GOLD, Global initiative for Obstructive Lung Disease; BMI, body mass index; CAT, COPD Assessment Test; mMRC, modified Medical Research Council.

Table 4 Interactions between COPD stage, comorbidities, and dyspnea for annual direct or indirect costs

Model variables	Direct costs		Indirect costs
	n=2,090		n=773
	Exp(beta)	p-value	Exp(beta)	p-value
COPD
Stage 1/2	Ref		Ref
Stage 3/4	1.69	<0.0001	1.35	0.10
Comorbidities
Low number (<3)	Ref		Ref
High number (≥3)	1.83	<0.0001	1.46	0.03
Dyspnea
Low level (mMRC <2)	Ref		Ref
High level (mMRC ≥2)	1.43	<0.0001	1.46	0.10
Interactions
COPD stage 3/4 × high number of comorbidities	0.72	0.0001	0.87	0.57
COPD stage 3/4 × high level of dyspnea	1.03	0.75	1.02	0.94
High level of dyspnea × high number of comorbidities	1.05	0.56	0.90	0.68

Notes: Models were adjusted for age group, sex, education, smoking status, and BMI class. Estimates with p<0.05 are in bold.

Abbreviation: mMRC, modified Medical Research Council.

Figure 2 Adjusted mean total direct or indirect costs (€) per year for subgroups.

Note: Means were adjusted according to regression models shown in Table 4.
Abbreviations: GOLD, Global initiative for Obstructive Lung Disease; mMRC, modified Medical Research Council.

Table S1 German unit costs

Sources of costs	Unit costs (€)per day/visit
Direct costs categories
GP or GP for internal medicine	20.22
Specialists
Specialist for internal medicine (including pneumologist)	64.65
Gynecologist	30.53
Ophthalmologist	35.09
Orthopedist	25.27
Otorhinolaryngologist	27.55
Surgeon	44.11
Dermatologist	19.10
Radiologist	43.97
Urologist	24.97
Neurologist/psychiatrist/psychotherapist	45.58
Specialist in occupational medicine	20.22
Other physician (including ambulant hospital visits)	43.97
Rehabilitation
Ambulant visit	48.29
Inpatient rehabilitation	122.09
Hospital treatment
Ambulant visit	43.97
Inpatient hospital	589.32
Physiotherapist	16.62
Prescribed pharmaceuticals	AOK Institute
Indirect cost categoriesa
Work absenceb	177.21
Premature retirement	37,126 (per year)

Notes: German unit costs by Bock et al¹ were calculated based on regularly published sources from different players in the German health care system (mainly accounting data and official statistics; differences between statutory and private health insurance were considered) and represent an approximation of societal opportunity cost. An annual update is provided by Bock et al.

a Indirect costs only for subjects of employable age <65 years.

b Work absence only for full-time and regular part-time employees.

Abbreviation: GP, general practitioner.

BockJOBrettschneiderCSeidlHCalculation of standardised unit costs from a societal perspective for health economic evaluationGesundheitswesen20157715361 German25025287

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