Lung and kidney: a dangerous liaison? A population-based cohort study in COPD patients in Italy

Figures & data

Figure 1 Schematic design of the enrollment and follow-up of COPD patients.

Abbreviation: ICD-9-CM, International Classification of Diseases, 9th Revision, Clinical Modification.

Table 1 Study subjects at baseline: demographics, severity of disease, and associated comorbidities

Population features	45–64 years (n=2,537) (%)	65–74 years (n=5,984) (%)	75–84 years (n=11,817) (%)	≥85 years (n=6,934) (%)	All patients (n=27,272) (%)
Male gender	68.7	69.3	62.9	46.5	60.7
Severity score
0	67.6	65.4	66.7	72.4	68.0
1	29.7	30.6	29.4	25.2	28.6
2	2.7	4.0	3.9	2.4	3.4
Modified Charlson index
0	44.9	35.3	30.2	30.5	32.8
1	35.2	36.9	39.1	40.6	38.6
2	14.1	18.9	21.5	20.9	20.1
≥3	5.8	9.0	9.3	8.0	8.6
Selected comorbidities
CKD	4.3	8.1	10.5	13.6	10.2
Heart failure	11.9	18.9	26.1	32.6	24.9
Ischemic heart disease	8.3	9.9	9.0	7.6	8.8
Cerebrovascular diseases	4.5	8.1	11.3	12.3	10.2
Peripheral arterial disease	6.0	8.6	8.5	5.4	7.5
Diabetes	24.3	25.9	23.7	20.2	23.4
Neoplasms	16.8	23.6	22.8	15.7	20.6
Dementia	0.4	1.8	4.8	10.5	5.2
Liver diseases	5.2	3.4	1.6	0.8	2.1
Peptic ulcer	1.4	1.4	1.5	1.6	1.5
Rheumatologic diseases	2.1	2.0	2.3	1.3	1.9

Notes: Severity score was defined by none, one, or both of the following criteria: a hospital diagnosis or an exemption from medical charges due to respiratory failure; previous hospitalizations for COPD. Modified Charlson index: the modified version of the Charlson Comorbidity Index (CCI) adapted to ICD-9-CM codes was adopted based on diseases reported during hospitalizations.

Abbreviations: CKD, chronic kidney disease; ICD-9-CM, International Classification of Diseases, 9th Revision, Clinical Modification.

Table 2 Most common causes of death among 16,288 decedents in the cohort of COPD patients

Cause of death (ICD-10-CM)	n	%
Diseases of the respiratory system (J00–J99)	3,720	22.8
COPD (J40–J44, J47)	2,652	16.3
Asthma (J45–J46)	28	0.2
Other respiratory diseases (J00–J39, J50–J99)	1,040	6.4
Circulatory diseases (I00–I99)	6,112	37.5
Hypertensive diseases (I10–I15)	810	5.0
Ischemic heart diseases (I20–I25)	2,410	14.8
Other heart diseases (I00–I09, I26–I51)	1,714	10.5
Cerebrovascular diseases (I60–I69)	956	5.9
Other circulatory diseases (I70–I99)	224	1.4
Neoplasms (C00–D48)	3,604	22.1
Lung cancer (C33–C34)	1,559	9.6
Other neoplasms (C00–C32, C35–D48)	2,045	12.6
Diabetes (E10–E14)	419	2.6
Dementia, Alzheimer’s disease (F01–F03, G30)	474	2.9
Diseases of the digestive system (K00–K99)	553	3.4
Other causes of death	1,406	8.6

Abbreviation: ICD-10-CM, International Classification of Diseases, 10th Revision, Clinical Modification.

Table 3 Patients discharged with a diagnosis of COPD: hazard ratios (HRs) with 95% CI for overall mortality estimated by Cox regression

Population features	Overall cohort		Patients aged 45–84 years
	HR (CI)	P-value	HR (CI)	P-value
Age, years	1.07 (1.06–1.07)	<0.001	1.06 (1.06–1.06)	<0.001
Females vs males	0.76 (0.73–0.78)	<0.001	0.74 (0.71–0.77)	<0.001
Severity score 1 vs 0	1.39 (1.34–1.44)	<0.001	1.45 (1.40–1.51)	<0.001
Severity score 2 vs 0	1.69 (1.57–1.82)	<0.001	1.83 (1.68–1.99)	<0.001
Charlson 1 vs 0	1.31 (1.26–1.36)	<0.001	1.39 (1.32–1.45)	<0.001
Charlson 2 vs 0	1.57 (1.50–1.64)	<0.001	1.70 (1.61–1.80)	<0.001
Charlson 3+ vs 0	1.84 (1.74–1.95)	<0.001	1.99 (1.86–2.13)	<0.001
CKD	1.36 (1.30–1.42)	<0.001	1.41 (1.33–1.50)	<0.001

Notes: Severity score was defined by none, one, or both of the following criteria: an hospital diagnosis or an exemption from medical charges due to respiratory failure; previous hospitalizations for COPD. Modified Charlson index: the modified version of the Charlson Comorbidity Index (CCI) adapted to ICD-9-CM codes was adopted based on diseases reported during hospitalizations.

Abbreviations: HR, hazard ratio; CI, confidence interval; CKD, chronic kidney disease; ICD-9-CM, International Classification of Diseases, 9th Revision, Clinical Modification.

Figure 2 Survival curves for COPD patients with and without chronic kidney disease (CKD).