Cardiol Res

Cardiology Research, ISSN 1923-2829 print, 1923-2837 online, Open Access

Article copyright, the authors; Journal compilation copyright, Cardiol Res and Elmer Press Inc

Journal website https://cr.elmerpub.com

Original Article

Volume 16, Number 4, August 2025, pages 366-372

Weight Bearing Index Is Associated With Length of Hospital Stay in Patients Undergoing Cardiac Surgery

Figure 1. A logistic regression analysis for independent predictors of the length of hospital stay. A logistic regression analysis was performed to identify independent predictors of the length of hospital stay by WBI using age, sex, BMI, and delirium. The length of hospital stay was cut by the median value of 23. OR: odds ratio, BMI: body mass index, WBI: weight bearing index.

**Table 1.** Baseline Characteristics in the Low and Preserved WBI Groups
Variables	All	Low WBI	Preserved WBI	P value
There were no missing values. The P value reflects the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; BMI: body mass index; COPD: chronic obstructive pulmonary disease.
Age, year	69.0 (59.0 - 75.0)	70.5 (62.5 - 76.0)	68.0 (58.0 - 73.0)	0.094
Male, n (%)	80 (74.1)	28 (58.3)	52 (86.7)	0.001
Height, cm	163 ± 9	161 ± 9	165 ± 9	0.026
Weight, kg	62.2 ± 11.9	62.7 ± 13.3	61.8 ± 10.7	0.714
BMI, kg/m²	23.4 ± 3.5	24.1 ± 3.8	22.8 ± 3.2	0.051
Underlying diseases
Hypertension, n (%)	86 (79.6)	40 (83.3)	46 (76.7)	0.393
Diabetes mellitus, n (%)	36 (33.3)	18 (37.5)	18 (30.0)	0.411
Dyslipidemia, n (%)	72 (66.7)	34 (70.8)	38 (63.3)	0.411
COPD, n (%)	9 (8.3)	4 (8.3)	5 (8.3)	1

Table 1. Baseline Characteristics in the Low and Preserved WBI Groups

Variables

All

Low WBI

Preserved WBI

P value

N = 108

N = 48

N = 60

There were no missing values. The P value reflects the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; BMI: body mass index; COPD: chronic obstructive pulmonary disease.

Age, year

69.0 (59.0 - 75.0)

70.5 (62.5 - 76.0)

68.0 (58.0 - 73.0)

0.094

Male, n (%)

80 (74.1)

28 (58.3)

52 (86.7)

0.001

Height, cm

163 ± 9

161 ± 9

165 ± 9

0.026

Weight, kg

62.2 ± 11.9

62.7 ± 13.3

61.8 ± 10.7

0.714

BMI, kg/m²

23.4 ± 3.5

24.1 ± 3.8

22.8 ± 3.2

0.051

Underlying diseases

Hypertension, n (%)

86 (79.6)

40 (83.3)

46 (76.7)

0.393

Diabetes mellitus, n (%)

36 (33.3)

18 (37.5)

18 (30.0)

0.411

Dyslipidemia, n (%)

72 (66.7)

34 (70.8)

38 (63.3)

0.411

COPD, n (%)

9 (8.3)

4 (8.3)

5 (8.3)

**Table 2.** Operative Procedures in the Low and Preserved WBI Groups
Variables	All	Low WBI	Preserved WBI	P value
^aValve operation included valve replacement and valvuloplasty. ^bOthers included patent foramen ovale closure, partial lung resection, and Morrow surgery. There were no missing values. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; CABG: coronary artery bypass grafting; LAC: left atrial appendage closure; PVI: pulmonary vein isolation.
Valve operation, n (%)^a	62 (57.4)	27 (56.3)	35 (58.3)	0.828
CABG, n (%)	59 (54.6)	28 (58.3)	31 (51.7)	0.489
LAC, n (%)	25 (23.1)	15 (31.3)	10 (16.7)	0.074
PVI, n (%)	12 (11.1)	6 (12.5)	6 (10.0)	0.681
Others, n (%)^b	5 (4.6)	2 (4.2)	3 (5.0)	0.838

Table 2. Operative Procedures in the Low and Preserved WBI Groups

Variables

All

Low WBI

Preserved WBI

P value

N = 108

N = 48

N = 60

^aValve operation included valve replacement and valvuloplasty. ^bOthers included patent foramen ovale closure, partial lung resection, and Morrow surgery. There were no missing values. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; CABG: coronary artery bypass grafting; LAC: left atrial appendage closure; PVI: pulmonary vein isolation.

Valve operation, n (%)^a

62 (57.4)

27 (56.3)

35 (58.3)

0.828

CABG, n (%)

59 (54.6)

28 (58.3)

31 (51.7)

0.489

LAC, n (%)

25 (23.1)

15 (31.3)

10 (16.7)

0.074

PVI, n (%)

12 (11.1)

6 (12.5)

6 (10.0)

0.681

Others, n (%)^b

5 (4.6)

2 (4.2)

3 (5.0)

0.838

**Table 3.** Preoperative Examinations in the Low and Preserved WBI Groups
Variables	All	Missing^a	Low WBI	Missing^a	Preserved WBI	Missing	P value
^aMissing means missing value. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; VC: vital capacity; FEV1: forced expiratory volume % in 1 s; AST: aspartate aminotransferase; ALT: alanine aminotransferase; LDH: lactate dehydrogenase; BUN: urea nitrogen; eGFR: estimated glomerular filtration rate; BNP: brain natriuretic peptide; LAD: left atrial diameter; LDVd: left ventricular diastolic diameter; LVDs: left ventricular systolic diameter; LVEF: left ventricular ejection fraction; TRPG: tricuspid regurgitation pressure gradient.
Spirometry
VC, %	96.1 ± 13.8	13	92.5 ± 13.6	4	99.1 ± 12.9	9	0.020
FEV1, %	78.0 (69.8 - 91.4)	13	78.0 (71.4 - 91.4)	4	74.5 (68.9 - 91.1)	9	0.354
Laboratory examinations
Hemoglobin, g/dL	13.1 ± 1.9	0	12.9 ± 1.8	0	13.3 ± 1.9	0	0.266
Total protein, g/dL	7.02 ± 0.53	0	7.05 ± 0.54	0	7.00 ± 0.54		0.609
Albumin, g/dL	4.07 ± 0.43	0	4.07 ± 0.38	0	4.08 ± 0.46	0	0.837
AST, U/L	23.0 (18.5 - 29.5)	0	21.5 (19.0 - 25.5)	0	24.5 (18.0 - 33.0)	0	0.074
ALT, U/L	19.0 (14.0 - 32.0)	0	18.0 (14.0 - 23.5)	0	21.5 (14.0 - 34.0)	0	0.122
LDH, U/L	196 (172 - 223)	0	190 (170 - 220)	0	203 (177 - 226)	0	0.291
BUN, mg/dL	18.0 (15.0 - 23.0)	1	18.5 (14.5 - 22.5)	0	18.0 (16.0 - 23.0)	1	0.965
Creatinine, mg/dL	0.95 (0.83 - 1.19)	0	0.90 (0.81 - 1.18)	0	0.98 (0.84 - 1.19)	0	0.174
eGFR, mL/min/1.73m²	56.6 ± 21.4	0	57.5 ± 19.6	0	55.9 ± 22.9	0	0.705
Hemoglobin A1c, %	5.85 (5.60 - 6.60)	6	5.90 (5.50 - 6.70)	2	5.85 (5.60 - 6.35)	4	0.917
BNP, pg/mL	124 (48 - 293)	3	207 (57 - 305)	2	104 (48 - 243)	1	0.252
Echocardiography
LAD, mm	42.0 (36.8 - 48.0)	0	41.4 (36.7 - 47.2)	0	43.0 (37.5 - 48.7)	0	0.583
LVDd, mm	51.5 ± 9.4	0	49.6 ± 9.6	0	53.1 ± 9.0	0	0.054
LVDs, mm	34.4 (29.3 - 42.9)	0	3.05 (29.7 - 41.8)	0	33.8 (28.8 - 43.9)	0	0.798
LVEF, %	60.9 (46.1 - 67.9)	0	58.1 (47.3 - 67.8)	0	63.1 (45.4 - 70.0)	0	0.611
TRPG, mm Hg	19.9 ± 13.1	2	17.3 ± 12.3	1	22.0 ± 13.5	1	0.063
E/e’	13.5 (9.7 - 18.1)	10	13.9 (10.1 - 21.1)	6	12.3 (9.1 - 16.8)	4	0.316

Table 3. Preoperative Examinations in the Low and Preserved WBI Groups

Variables

All

Missing^a

Low WBI

Missing^a

Preserved WBI

Missing

P value

N = 108

N = 48

N = 60

^aMissing means missing value. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; VC: vital capacity; FEV1: forced expiratory volume % in 1 s; AST: aspartate aminotransferase; ALT: alanine aminotransferase; LDH: lactate dehydrogenase; BUN: urea nitrogen; eGFR: estimated glomerular filtration rate; BNP: brain natriuretic peptide; LAD: left atrial diameter; LDVd: left ventricular diastolic diameter; LVDs: left ventricular systolic diameter; LVEF: left ventricular ejection fraction; TRPG: tricuspid regurgitation pressure gradient.

Spirometry

VC, %

96.1 ± 13.8

92.5 ± 13.6

99.1 ± 12.9

0.020

FEV1, %

78.0 (69.8 - 91.4)

78.0 (71.4 - 91.4)

74.5 (68.9 - 91.1)

0.354

Laboratory examinations

Hemoglobin, g/dL

13.1 ± 1.9

12.9 ± 1.8

13.3 ± 1.9

0.266

Total protein, g/dL

7.02 ± 0.53

7.05 ± 0.54

7.00 ± 0.54

0.609

Albumin, g/dL

4.07 ± 0.43

4.07 ± 0.38

4.08 ± 0.46

0.837

AST, U/L

23.0 (18.5 - 29.5)

21.5 (19.0 - 25.5)

24.5 (18.0 - 33.0)

0.074

ALT, U/L

19.0 (14.0 - 32.0)

18.0 (14.0 - 23.5)

21.5 (14.0 - 34.0)

0.122

LDH, U/L

196 (172 - 223)

190 (170 - 220)

203 (177 - 226)

0.291

BUN, mg/dL

18.0 (15.0 - 23.0)

18.5 (14.5 - 22.5)

18.0 (16.0 - 23.0)

0.965

Creatinine, mg/dL

0.95 (0.83 - 1.19)

0.90 (0.81 - 1.18)

0.98 (0.84 - 1.19)

0.174

eGFR, mL/min/1.73m²

56.6 ± 21.4

57.5 ± 19.6

55.9 ± 22.9

0.705

Hemoglobin A1c, %

5.85 (5.60 - 6.60)

5.90 (5.50 - 6.70)

5.85 (5.60 - 6.35)

0.917

BNP, pg/mL

124 (48 - 293)

207 (57 - 305)

104 (48 - 243)

0.252

Echocardiography

LAD, mm

42.0 (36.8 - 48.0)

41.4 (36.7 - 47.2)

43.0 (37.5 - 48.7)

0.583

LVDd, mm

51.5 ± 9.4

49.6 ± 9.6

53.1 ± 9.0

0.054

LVDs, mm

34.4 (29.3 - 42.9)

3.05 (29.7 - 41.8)

33.8 (28.8 - 43.9)

0.798

LVEF, %

60.9 (46.1 - 67.9)

58.1 (47.3 - 67.8)

63.1 (45.4 - 70.0)

0.611

TRPG, mm Hg

19.9 ± 13.1

17.3 ± 12.3

22.0 ± 13.5

0.063

E/e’

13.5 (9.7 - 18.1)

13.9 (10.1 - 21.1)

12.3 (9.1 - 16.8)

0.316

**Table 4.** Pre- and Postoperative Physical Functions in the Low and Preserved WBI Groups
Variables	All	Missing	Low WBI	Missing	Preserved WBI	Missing	P value
P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; SPPB: Short Physical Performance Battery.
Preoperative
Grip strength, kg	28.0 ± 9.2	0	24.1 ± 8.5	0	31.0 ± 8.7	0	< 0.001
Quadriceps strength, kg	27.4 (20.2 - 37.8)	0	20.0 (17.4 - 22.7)	0	37.2 (30.4 - 47.1)	0	< 0.001
One-leg standing time, s	27.6 (12.1 - 57.5)	0	16.9 (7.1 - 37.1)	0	48.0 (20.1 - 60.0)	0	< 0.001
10-m walking speed, m/s	1.57 ± 0.37	0	1.38 ± 0.32	0	1.72 ± 0.34	0	< 0.001
SPPB, score	12.0 (11.0 - 12.0)	1	12.0 (10.0 - 12.0)	1	12.0 (12.0 - 12.0)	0	< 0.001
2-min walking distance, m	182 (163 - 200)	21	170 (150 - 181)	8	194 (180 - 204)	13	< 0.001
Postoperative
Grip strength, kg	24.6 ± 9.2	0	21.0 ± 8.0	0	27.5 ± 9.2	0	< 0.001
Quadriceps strength, kg	25.7 (18.3 - 34.1)	0	18.9 (14.8 - 25.6)	0	32.8 (25.4 - 41.8)	0	< 0.001
One-leg standing time, s	21.9 (8.3 - 58.0)	0	15.6 (6.1 - 37.8)	0	39.1 (13.1 - 60.0)	0	0.002
10m walking speed, m/s	1.47 ± 0.38	0	1.31 ± 0.35	0	1.6.0 ± 0.35	0	< 0.001
SPPB, score	12.0 (11.0 - 12.0)	1	12.0 (10.0 - 12.0)	1	12.0 (11.0 - 12.0)	0	0.02
2-min walking distance, m	170 (146 - 195)	22	160 (130 - 179)	9	184 (153 - 200)	13	0.001

Table 4. Pre- and Postoperative Physical Functions in the Low and Preserved WBI Groups

Variables

All

Missing

Low WBI

Missing

Preserved WBI

Missing

P value

N = 108

N = 48

N = 60

P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; SPPB: Short Physical Performance Battery.

Preoperative

Grip strength, kg

28.0 ± 9.2

24.1 ± 8.5

31.0 ± 8.7

< 0.001

Quadriceps strength, kg

27.4 (20.2 - 37.8)

20.0 (17.4 - 22.7)

37.2 (30.4 - 47.1)

< 0.001

One-leg standing time, s

27.6 (12.1 - 57.5)

16.9 (7.1 - 37.1)

48.0 (20.1 - 60.0)

< 0.001

10-m walking speed, m/s

1.57 ± 0.37

1.38 ± 0.32

1.72 ± 0.34

< 0.001

SPPB, score

12.0 (11.0 - 12.0)

12.0 (10.0 - 12.0)

12.0 (12.0 - 12.0)

< 0.001

2-min walking distance, m

182 (163 - 200)

170 (150 - 181)

194 (180 - 204)

< 0.001

Postoperative

Grip strength, kg

24.6 ± 9.2

21.0 ± 8.0

27.5 ± 9.2

< 0.001

Quadriceps strength, kg

25.7 (18.3 - 34.1)

18.9 (14.8 - 25.6)

32.8 (25.4 - 41.8)

< 0.001

One-leg standing time, s

21.9 (8.3 - 58.0)

15.6 (6.1 - 37.8)

39.1 (13.1 - 60.0)

0.002

10m walking speed, m/s

1.47 ± 0.38

1.31 ± 0.35

1.6.0 ± 0.35

< 0.001

SPPB, score

12.0 (11.0 - 12.0)

12.0 (10.0 - 12.0)

12.0 (11.0 - 12.0)

0.02

2-min walking distance, m

170 (146 - 195)

160 (130 - 179)

184 (153 - 200)

0.001

**Table 5.** Clinical Outcomes in the Low and Preserved WBI Groups
Variables	All	Low WBI	Preserved WBI	P value
There were no missing values. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; NYHA: New York Heart Association; METs: metabolic equivalents.
Start of cardiac rehabilitation, hospital days	1.0 (1.0 - 1.0)	1.0 (1.0 - 1.0)	1.0 (1.0 - 1.5)	0.826
End sitting position, hospital days	2.0 (2.0 - 3.0)	2.0 (2.0 - 4.0)	2.0 (2.0 - 3.0)	0.387
Ambulation, hospital days	2.5 (2.0 - 4.0)	3.0 (2.0 - 4.0)	2.0 (2.0 - 4.0)	0.757
Walking, hospital days	4.0 (3.0 - 5.0)	4.0 (3.0 - 5.0)	3.5 (3.0 - 5.0)	0.510
Delirium, n (%)	6 (5.6)	1 (2.1)	5 (8.3)	0.159
Hospitalization, days	23.0 (20.5 - 27.0)	24.5 (22.0 - 27.5)	22.0 (20.0 - 27.0)	0.022
Hospital transfer, n (%)	7 (6.5)	4 (8.3)	3 (5.0)	0.485
NYHA class at discharge	1 (1 - 2)	1 (1 - 2)	1 (1 - 1)	0.030
METs at discharge, METs	3.1 (2.9 - 3.5)	3.0 (2.7 - 3.3)	3.25 (2.9 - 3.6)	0.006

Table 5. Clinical Outcomes in the Low and Preserved WBI Groups

Variables

All

Low WBI

Preserved WBI

P value

N = 108

N = 48

N = 60

There were no missing values. P value refers to the comparison between the low WBI and preserved WBI groups. WBI: weight bearing index; NYHA: New York Heart Association; METs: metabolic equivalents.

Start of cardiac rehabilitation, hospital days

1.0 (1.0 - 1.0)

1.0 (1.0 - 1.5)

0.826

End sitting position, hospital days

2.0 (2.0 - 3.0)

2.0 (2.0 - 4.0)

2.0 (2.0 - 3.0)

0.387

Ambulation, hospital days

2.5 (2.0 - 4.0)

3.0 (2.0 - 4.0)

2.0 (2.0 - 4.0)

0.757

Walking, hospital days

4.0 (3.0 - 5.0)

3.5 (3.0 - 5.0)

0.510

Delirium, n (%)

6 (5.6)

1 (2.1)

5 (8.3)

0.159

Hospitalization, days

23.0 (20.5 - 27.0)

24.5 (22.0 - 27.5)

22.0 (20.0 - 27.0)

0.022

Hospital transfer, n (%)

7 (6.5)

4 (8.3)

3 (5.0)

0.485

NYHA class at discharge

1 (1 - 2)

1 (1 - 1)

0.030

METs at discharge, METs

3.1 (2.9 - 3.5)

3.0 (2.7 - 3.3)

3.25 (2.9 - 3.6)

0.006