Table 1. Characteristics of patients hospitalized for acute exacerbation of chronic obstructive pulmonary disease by acute kidney injury
|
AKI
|
Non-AKI
|
|
Characteristics
|
n=24,833
(7.0%)
|
n=332,157
(93.0%)
|
P value
|
Age (year), median (IQR)
|
76 (67-83)
|
70 (60-80)
|
<0.001
|
Male
|
12,605 (50.8)
|
136,949 (41.2)
|
<0.001
|
Race/ethnicity
|
|
|
<0.001
|
Non-Hispanic white
|
17,375 (72.3)
|
237,741 (74.0)
|
|
Non-Hispanic black
|
2,848 (11.9)
|
34,030(10.6)
|
|
Hispanic
|
2,593 (10.8)
|
35,333(11.0)
|
|
Others
|
1,217 (5.1)
|
14,034 (4.5)
|
|
Primary health insurance
|
|
|
<0.001
|
Medicare
|
20,089 (81.4)
|
233,472 (70.3)
|
|
Medicaid
|
1,817 (7.4)
|
36,878 (11.1)
|
|
Private
|
1,682 (6.8)
|
38,944 (11.7)
|
|
Others
|
1,093 (4.4)
|
22,698 (6.9)
|
|
Median household income quartile
|
|
|
<0.001
|
1 (lowest)
|
7,216 (29.7)
|
103,211 (31.9)
|
|
2
|
6,230 (25.6)
|
89,605 (27.7)
|
|
3
|
5,931 (24.4)
|
76,312 (23.6)
|
|
4 (highest)
|
4,927 (20.3)
|
54,794 (16.9)
|
|
Patient residence
|
|
|
<0.001
|
Metropolitan
|
22,529 (90.8)
|
288,858 (87.0)
|
|
Non-metropolitan
|
2,304 (9.2)
|
43,299 (13.0)
|
|
Selected comorbidities*
|
|
|
|
Congestive heart failure
|
11,326 (45.6)
|
78,120 (23.5)
|
<0.001
|
Depression
|
3,348 (13.5)
|
52,482 (15.8)
|
<0.001
|
Diabetes
|
10,415 (41.9)
|
93,904 (28.3)
|
<0.001
|
Hypertension
|
20,125 (81.0)
|
219,396 (66.1)
|
<0.001
|
Obesity
|
5,048 (20.3)
|
50,795 (15.3)
|
<0.001
|
Peripheral artery disease
|
2,967 (11.9)
|
24,961 (7.5%)
|
<0.001
|
Hospital length-of-stay
|
|
|
<0.001
|
<3 days
|
3,599 (14.5)
|
97,877 (29.5)
|
|
3-4 days
|
7,223 (29.1)
|
117,624 (35.4)
|
|
5-6 days
|
5,407 (21.8)
|
60,523 (18.2)
|
|
≥7 days
|
8,604 (34.6)
|
56,133 (16.9)
|
|
Hospital state
|
|
|
<0.001
|
Arkansas
|
1,695 (6.8)
|
15,644 (4.7)
|
|
California
|
4,561 (18.4)
|
63,913 (19.2)
|
|
Florida
|
10,295 (41.5)
|
135,717 (40.9)
|
|
Iowa
|
764 (3.1)
|
11,825 (3.6)
|
|
Nebraska
|
536 (2.2)
|
7,252 (2.2)
|
|
New York
|
6,667 (26.8)
|
93,863 (28.3)
|
|
Utah
|
315 (1.3)
|
3,943 (1.2)
|
|
Abbreviations: AKI, acute kidney injury; IQR, interquartile range
Data are shown as n (%) unless otherwise specified
* Selected from 29 Elixhauser comorbidity measures and arrhythmia
Table 2. Hazard ratio for all-cause readmission during 30-day periods after index hospitalization for acute exacerbation of chronic obstructive sleep apnea, according to acute kidney injury, overall and stratified by age category and sex
|
30-day readmission rate
|
Unadjusted model
|
Adjusted model*
|
|
AKI
(n=24,833)
|
Non-AKI
(n=332,157)
|
HR (95% CI)
|
P-value
|
HR (95% CI)
|
P-value
|
Overall (n=356,990)
|
22.4%
|
15.8%
|
1.47 (1.43-1.51)
|
<0.001
|
1.07 (1.04-1.11)
|
<0.001
|
Age category
|
|
|
|
|
|
|
40-64 years (n=122,362)
|
20.9%
|
14.0%
|
1.52 (1.43-1.63)
|
<0.001
|
1.03 (0.96-1.10)
|
0.45
|
≥65 years (n=234,628)
|
22.7%
|
16.8%
|
1.41 (1.36-1.45)
|
<0.001
|
1.09 (1.05-1.13)
|
<0.001
|
Sex†
|
|
|
|
|
|
|
Men (n=149,333)
|
22.0%
|
16.7%
|
1.36 (1.30-1.41)
|
<0.001
|
1.03 (0.99-1.08)
|
0.14
|
Women (n=207,436)
|
22.7%
|
15.2%
|
1.56 (1.50-1.62)
|
<0.001
|
1.12 (1.07-1.17)
|
<0.001
|
Abbreviations: AKI, acute kidney injury; HR, hazard ratio; CI, confidence interval
* Cox proportional hazards model adjusting for age, sex, race/ethnicity, insurance status, estimated household income, residential status, hospital length-of-stay, hospital state, and Elixhauser comorbidity measures and arrhythmia with generalized estimating equations to account for patient clustering within hospitals
‡ 221 patients with missingness on sex data
Table 3. Hazard ratio for all-cause readmission during 90-day periods after index hospitalization for acute exacerbation of chronic obstructive sleep apnea, according to acute kidney injury, overall and stratified by age category and sex
|
90-day Readmission rate
|
Unadjusted model
|
Adjusted model*
|
|
AKI
(n=24,833)
|
Non-AKI
(n=332,157)
|
HR (95% CI)
|
P-value
|
HR (95% CI)
|
P-value
|
Overall (n=356,990)
|
39.7%
|
31.0%
|
1.35 (1.32-1.38)
|
<0.001
|
1.03 (1.00-1.05)
|
0.04
|
Age category
|
|
|
|
|
|
|
40-64 years (n=122,362)
|
37.6%
|
27.8%
|
1.43 (1.36-1.50)
|
<0.001
|
1.00 (0.95-1.06)
|
0.86
|
≥65 years (n=234,628)
|
40.2%
|
32.8%
|
1.29 (1.26-1.32)
|
<0.001
|
1.03 (1.00-1.06)
|
0.03
|
Sex†
|
|
|
|
|
|
|
Men (n=149,333)
|
38,9%
|
32.2%
|
1.26 (1.22-1.29)
|
<0.001
|
0.99 (0.96-1.03)
|
0.59
|
Women (n=207,436)
|
40.5%
|
30.2%
|
1.43 (1.39-1.48)
|
<0.001
|
1.06 (1.02-1.09)
|
0.001
|
Abbreviations: AKI, acute kidney injury; HR, hazard ratio; CI, confidence interval
* Cox proportional hazards model adjusting age, sex, race/ethnicity, insurance status, estimated household income, residential status, hospital length-of-stay, hospital state, and Elixhauser comorbidity measures and arrhythmia with generalized estimating equations to account for patient clustering within hospitals
† 221 patients with missingness on sex data
Table 4. The ten most frequent principal diagnoses of readmissions in patient hospitalized for acute exacerbation of chronic obstructive pulmonary disease, overall and stratified by acute kidney injury
Without AKI (n=50,984)
|
With AKI (n=8,151)
|
Primary diagnosis*
|
n (%)
|
Primary diagnosis*
|
n (%)
|
COPD and bronchiectasis
|
12,954 (25.4)
|
Septicemia
|
1,176 (14.4)
|
Pneumonia
|
3,947 (7.7)
|
Acute renal failure
|
963 (11.8)
|
Respiratory failure
|
3,571 (7.0)
|
COPD and bronchiectasis
|
944 (11.6)
|
Asthma
|
3,255 (6.4)
|
Congestive heart failure
|
713 (8.8)
|
Congestive heart failure
|
3.019 (5.9)
|
Respiratory failure
|
623 (7.6)
|
Septicemia
|
1,806 (3.5)
|
Pneumonia
|
579 (7.1)
|
Cardiac dysrhythmia
|
1,395 (2.7)
|
Asthma
|
204 (2.5)
|
Nonspecific chest pain
|
921 (1.8)
|
Acute myocardial infarction
|
166 (2.0)
|
Aspiration pneumonitis
|
683 (1.3)
|
Nonspecific chest pain
|
166 (2.0)
|
Fluid and electrolyte disorders
|
666 (1.3)
|
Intestinal infection
|
158 (1.9)
|
*The primary diagnoses (>14,000 ICD-9-CM diagnosis codes) consolidated into 285 mutually exclusive diagnostic categories by using the AHRQ-defined Clinical Classifications Software.