Table 1 Baseline characteristics of the study population in NIS databases

Age (mean ± std err)

76.09 ± 0.09

77.26 ± 0.37

76.12 ± 0.08

0.002

Gender

< 0.001

 Male

58.06

69.38

58.40

 Female

41.94

30.62

41.60

Race/ethnicity

0.300

 White

87.59

86.91

87.57

 Black

4.09

4.74

4.11

 Hispanic

4.94

4.46

4.93

 Asian or pacific islander

1.36

2.51

1.39

 Native American

0.33

0.56

0.33

 Others

1.69

0.84

1.67

Comorbidity

 Coronary artery disease

49.67

51.76

49.74

0.428

 Prior cerebrovascular disease

27.23

22.76

27.10

0.060

 Prior CABG

14.38

13.82

14.37

0.762

 Heart failure

39.05

42.01

39.14

0.257

 Mitral valve stenosis

0.22

0.27

0.22

0.846

 Valvular disease

20.82

20.87

20.82

0.981

 Hypertension

86.86

87.26

86.87

0.824

 Diabetes mellitus

35.01

34.15

34.99

0.725

 Obesity

16.94

16.53

16.93

0.829

 Chronic pulmonary disease

21.96

18.97

21.87

0.166

 Pulmonary circulation disorders

6.24

7.59

6.28

0.280

 Liver disease

2.55

2.44

2.55

0.891

 Renal failure

23.58

28.73

23.74

0.021

 Peripheral vascular disease

16.28

17.62

16.32

0.489

 Anemia

4.83

7.59

4.91

0.015

 Coagulopathy

3.71

14.09

4.02

< 0.001

 Alcohol dependent disorder

1.38

1.90

1.39

0.394

 Hyperthyroidism

0.43

0.54

0.43

0.740

Median household income

0.001

 0-25th percentile

21.77

15.85

21.59

 26-50th percentile

25.92

24.04

25.86

 51-75th percentile

27.96

27.05

27.94

 76-100th percentile

24.35

33.06

24.62

Primary payer

0.453

 Medicare/Medicaid

90.01

91.28

90.05

 Private insurance

7.89

7.90

7.89

 Self-pay

0.47

0.00

0.46

 Other

1.62

0.82

1.60

Hospital characteristics

 Hospital region

0.138

 Northeast

16.47

20.05

16.58

 Midwest

22.49

21.14

22.45

 South

39.22

34.42

39.07

 West

21.82

24.39

21.90

 Hospital bed size

0.624

 Small

10.61

10.30

10.60

 Medium

23.11

21.14

23.05

 Large

66.29

68.56

66.35

 Hospital teaching status

0.490

 Non-teaching

11.81

10.57

11.78

 Teaching

88.19

89.43

88.22

 Hospital location

0.044

 Urban

97.99

99.46

98.04

 Rural

2.01

0.54

1.96