Table 1 Demographic and clinical characteristics at baseline

Number of patients, n (N = 4899)

4899

100.0%

1681

34.3%

1932

39.4%

1286

26.3%

Age, mean (SD)

44.61

12.53

44.42

12.72

45.35

12.38

43.75

12.47

Age category, n (%)

  < 20

114

2.3%

33

2.0%

39

2.0%

42

3.3%

 20–64

4561

93.1%

1567

93.2%

1792

92.8%

1202

93.5%

 65–79

224

4.6%

81

4.8%

101

5.2%

42

3.3%

Female, n (%)

3456

70.5%

1152

68.5%

1394

72.2%

910

70.8%

Geographic region (Census Bureau), n (%)

 Northeast

1667

34.0%

684

40.7%

465

24.1%

518

40.3%

 Midwest

929

19.0%

188

11.2%

551

28.5%

190

14.8%

 West

677

13.8%

89

5.3%

306

15.8%

282

21.9%

 South

1624

33.1%

719

42.8%

609

31.5%

296

23.0%

Medicare coverage, n (%)

175

3.6%

61

3.6%

88

4.6%

26

2.0%

Year of index surgery, n (%)

 2007

388

7.9%

230

13.7%

148

7.7%

10

0.8%

 2008

442

9.0%

280

16.7%

151

7.8%

11

0.9%

 2009

528

10.8%

331

19.7%

192

9.9%

<10

 2010

638

13.0%

326

19.4%

278

14.4%

34

2.6%

 2011

718

14.7%

258

15.3%

323

16.7%

137

10.7%

 2012

599

12.2%

104

6.2%

282

14.6%

213

16.6%

 2013

575

11.7%

62

3.7%

232

12.0%

281

21.9%

 2014

619

12.6%

57

3.4%

208

10.8%

354

27.5%

   2015

392

8.0%

33

2.0%

118

6.1%

241

18.7%

Comorbid conditions,* n (%)

 Diabetes mellitus

2376

48.5%

814

48.4%

946

49.0%

616

47.9%

 Gastroesophageal reflux

1525

31.1%

444

26.4%

699

36.2%

382

29.7%

 Hypertension

2737

55.9%

898

53.4%

1147

59.4%

692

53.8%

 Sleep apnea

1291

26.4%

275

16.4%

593

30.7%

423

32.9%

 Deep vein thromboembolism

56

1.1%

19

1.1%

18

0.9%

19

1.5%

 Pulmonary embolism

55

1.1%

21

1.2%

17

0.9%

17

1.3%

 Dyslipidemia

2111

43.1%

742

44.1%

862

44.6%

507

39.4%

 Anxiety

456

9.3%

106

6.3%

204

10.6%

146

11.4%

 Depression

776

15.8%

189

11.2%

367

19.0%

220

17.1%

 Eating disorder

137

2.8%

27

1.6%

55

2.8%

55

4.3%

 Kidney disease

122

2.5%

30

1.8%

50

2.6%

42

3.3%

 Non-alcoholic fatty liver disease.

193

3.9%

35

2.1%

89

4.6%

69

5.4%

 Osteoarthritis

578

11.8%

198

11.8%

236

12.2%

144

11.2%

 Polycystic ovarian syndrome

149

3.0%

43

2.6%

60

3.1%

46

3.6%

 Psychotic disorder

433

8.8%

108

6.4%

196

10.1%

129

10.0%

 Substance use disorder

31

0.6%

<10

17

0.9%

<10

 Mixed Comorbidity Index score, mean (SD)

0.2

1.13

0.08

1.07

0.28

1.21

0.23

1.07

Mixed Comorbidity Index score, n (%)

  < 0

1379

28.1%

536

31.9%

521

27.0%

322

25.0%

 0

1997

40.8%

702

41.8%

750

38.8%

545

42.4%

  > 0

1523

31.1%

443

26.4%

661

34.2%

419

32.6%

 Hospital length of stay in days, mean (SD)

0.73

4.31

0.39

2.14

1.14

6.03

0.58

3.15