Table 3 Baseline characteristics stratified by BUN/ALB ratio

Hospitalization mortality (%)

30.5

1.9

 < 0.001

Age, years

80.5 ± 8.3

74.4 ± 9.6

 < 0.001

BMI, kg/m²

20.46 ± 3.83

21.10 ± 3.91

0.257

Sex, n (%)

0.518

 Male

50 (84.7)

211 (81.2)

 Female

9 (15.3)

49 (18.8)

Smoking status, n (%)

0.469

 Never smoked

10 (16.9)

55 (21.2)

 Current smoker/Ever smoked

49 (83.1)

205 (78.8)

Hospital stay, days

8.2 ± 4.2

7.9 ± 2.8

0.472

Exacerbations during preceding year, n (%)

27 (45.8)

115 (44.2)

0.831

GOLD stage, n (%)

0.485

 I

3 (5.0)

18 (6.9)

 II

27 (45.8)

94 (36.2)

 III

22 (37.3)

102 (39.2)

 IV

7 (11.9)

46 (17.7)

CHF, n (%)

26 (44.1)

71 (27.3)

0.012

RD, n (%)

37 (62.7)

114 (43.8)

0.009

Bronchiectasis, n (%)

16 (27.1)

79 (30.4)

0.620

Diabetes, n (%)

6 (10.2)

26 (10.0)

0.969

Hypertension, n (%)

40 (67.8)

136 (52.3)

0.031

CHD, n (%)

22 (37.3)

62 (23.8)

0.034

Neutrophil count, × 10⁹/L

10.27 (7.21–14.04)

6.58 (4.58–9.04)

0.001

Lymphocyte count, × 10⁹/L

0.85 (0.58–1.21)

1.22 (0.86–1.72)

 < 0.001

PH

7.38 ± 0.09

7.40 ± 0.05

0.239

PaO₂, mmHg

90.7 ± 29.0

89.4 ± 25.2

0.732

PaCO₂, mmHg

44.9 ± 14.3

45.2 ± 11.0

0.870

BUN, mmol/L

10.86 (7.10–12.25)

5.35 (4.14–7.40)

 < 0.001

ALB, g/L

32.69 ± 4.36

36.74 ± 4.28

 < 0.001