Data from 660 individuals who were admitted to the emergency department with a pneumonia diagnosis from August 2011 to June 2017 were extracted. Of the 125 excluded cases, 64 had other principal diagnoses (e.g., lung cancer, interstitial lung diseases), 33 were later classified as either hospital-acquired or health-care associated pneumonia, 5 had an incomplete record, 6 had cardiopulmonary arrest on admission, 4 consented to a do-not-resuscitate order, and 13 were either transferred from or transferred to another hospital. Thus, a total of 535 cases were left for analysis.
The median age (IQR) of patients was 79 (70-84) years, 369 of 535 (69.0%) were men, and all-cause, in-hospital mortality rate was 12 percent (Table 1). The cohort stayed for approximately 14 days in the hospital. In term of pneumonia severity, the majority was classified into the moderate group (338 individuals, 68.0%) whereas 100 patients (18.7%) had pneumonia at severe or extremely severe levels. The median CCI (IQR) was 1 (1-3) with roughly a quarter of the patients (131 individuals, 24.5%) scoring 2 points. The most common co-morbidities found in the CCI were malignancies (129 of 535, 24.1%), chronic pulmonary diseases (113 of 535, 21.1%) and congestive heart failure (103 of 535, 19.3%). In general, excluding cases with no record of comorbidities, there was a trend towards increasing mortality as the CCI score increased. The number rose from 6.8 percent in patients with CCI=1 to 25.0 percent with CCI = 5.
Table 1. General characteristics of study subjects
Characteristics
|
N = 535
|
Age in years, median (IQR)
|
79 (70-84)
|
Sex, male, n (%)
|
369 (69.0)
|
Length of stay in days, median (IQR)
|
14 (9-27)
|
Charlson Comorbidity Index, median (IQR)
|
1 (1-3)
|
In-hospital mortality, % (n/N)
|
12.2 (64/535)
|
Abbreviation: IQR, interquartile range
Univariable logistic regression modeling showed that older patients who presented with more severe pneumonia at admission were at higher risk for in-hospital death as each 1-year increase in age heightened the risk by 4 percent (odds ratio [OR] 1.04; 95% confidence interval [CI] 1.01 to 1.07). There was a trend towards increasing mortality in patients with malignancy, congestive heart failure, renal disease, diabetes with complication and dementia. The correlation between pneumonia severity and the CCI was weak, i.e., Spearman’s correlation coefficient=0.139, p=0.002. The multivariable regression model showed there was a tendency toward increasing mortality as A-DROP score increased but only in the extremely severe patients showed a significant difference. Among mild pneumonia patients, the prognostic impacts of CCI were marginally significant after adjustments for age and sex as a 1-point rise in CCI increased odds of death by 2-fold (OR 2.09; 95% CI 1.03-4.25). This impact, however, was reduced significantly as pneumonia severity increased (supplementary Table S1).
Considering a potential bias, we conducted the final analysis after excluding severe and extremely severe patients whose CCI was zero (60/353; 17.0%) and found that each per unit increase in CCI resulted in a 35% increase in odds of death (OR 1.35; 95% CI 1.16 to 1.58) (Table 2). Renal disease, followed by malignancy, showed the strongest association with mortality (OR 2.42; 95% CI 1.13 to 5.21 and OR 2.25; 95% CI 1.21 to 4.17). Age, sex, A-DROP categories, CCI and their interaction terms were added as predictors for multivariate analysis but no meaningful interactions were observed. The prognostic impacts of CCI were consistent across pneumonia severity categories and a 1-point increase in CCI increased odds of death by 28 percent (OR 1.28; 95% CI 1.07-1.53) (Table 3).
Table 2. Univariate analysis for in-hospital mortality
Variables
|
n (%)
|
OR (95% CI)
|
p-value
|
Age, yearsa
|
475 (88.8)
|
1.04 (1.01 – 1.07)
|
0.01
|
Sex
|
|
|
|
|
Male
|
329 (61.5)
|
reference
|
|
|
Female
|
146 (27.3)
|
1.18 (0.63 – 2.24)
|
0.61
|
Pneumonia severity
|
|
|
|
|
Mild
A-DROP=0
|
68 (12.7)
|
reference
|
|
|
Moderate
A-DROP=1-2
|
338 (63.2)
|
1.28 (0.43-3.80)
|
0.66
|
|
Severe
A-DROP=3
|
52 (9.7)
|
4.29 (1.28-14.39)
|
0.02
|
|
Extremely severe
A-DROP=4-5
|
17 (3.2)
|
11.20 (2.77-45.31)
|
<0.01
|
Charlson Comorbidity Index (CCI)b
|
475 (88.7)
|
1.35 (1.16-1.58)
|
<0.01
|
Charlson Comorbidity Index componentsc
|
Any malignancy
|
|
|
|
No
|
349 (73.5)
|
reference
|
|
Yes
|
126 (26.5)
|
2.25 (1.21-4.17)
|
0.01
|
Chronic pulmonary disease
|
|
|
|
No
|
367 (77.3)
|
reference
|
|
Yes
|
108 (22.7)
|
1.04 (0.51-2.13)
|
0.91
|
Congestive heart failure
|
|
|
|
No
|
375 (78.9)
|
reference
|
|
Yes
|
100 (21.1)
|
1.89 (0.98-3.65)
|
0.06
|
Renal disease
|
|
|
|
No
|
422 (88.8)
|
reference
|
|
Yes
|
53 (11.2)
|
2.42 (1.13-5.21)
|
0.02
|
Diabetes with complication
|
|
|
|
No
|
434 (91.4)
|
reference
|
|
Yes
|
41 (8.6)
|
2.03 (0.84-4.87)
|
0.11
|
Dementia
|
|
|
|
No
|
435 (91.6)
|
reference
|
|
Yes
|
40 (8.4)
|
2.10 (0.87-5.04)
|
0.10
|
Rheumatologic disease
|
|
|
|
No
|
459 (96.6)
|
reference
|
|
Yes
|
16 (3.4)
|
1.31 (0.29-5.97)
|
0.72
|
Mild liver disease
|
|
|
|
No
|
460 (96.8)
|
reference
|
|
Yes
|
15 (3.2)
|
0.64 (0.08-5.00)
|
0.67
|
Abbreviations: OR, odds ratio; CI, confidence interval
aOR for one year increasing in age; bOR for one point increasing in CCI; cConditions which has less than 10 cases were not analyzed.
Table 3. Multivariable logistic regression analysis for in-hospital mortality
Variables
|
No. of deaths/total number
|
B
|
OR (95% CI)
|
p-value
|
Age, yearsa
|
47/475
|
0.03
|
1.03 (0.99 – 1.07)
|
0.08
|
Sex
|
|
|
|
|
|
Male
|
31/329
|
|
reference
|
|
|
Female
|
16/146
|
0.34
|
1.41 (0.71-2.83)
|
0.33
|
Pneumonia severity
|
|
|
|
|
|
Mild
A-DROP=0
|
4/68
|
|
reference
|
|
|
Moderate
A-DROP=1-2
|
25/338
|
-0.31
|
0.73 (0.22-2.41)
|
0.61
|
|
Severe
A-DROP=3
|
11/52
|
0.59
|
1.80 (0.47-6.96)
|
0.39
|
|
Extremely severe
A-DROP=4-5
|
7/17
|
1.60
|
4.92 (1.11-21.98)
|
0.04
|
Charlson Comorbidity Index (CCI)b
|
47/475
|
0.25
|
1.28 (1.07-1.53)
|
<0.01
|
Abbreviations: B, beta coefficient; OR, odds ratio; CI, confidence interval
aOR for one year increasing in age; bOR for one point increasing in CCI