Table 1 Key Demographic and Baseline Characteristics of Individuals Participating in the NHANES between 2005 and 2008

Age(years)

48.000 (20.000–85.000)

40.000 (20.000–85.000)

46.000 (20.000–85.000)

50.000 (20.000–85.000)

59.500(20.000–85.000)

 < 0.001

BUN(mmol/L)

4.280(0.360–34.990)

2.860 (0.360–22.490)

3.930(1.790–20.350)

4.640(1.790–19.990)

6.070(2.860–34.990)

 < 0.001

CR(umol/L)

78.680(27.400–1573.520)

80.440 (28.290–1573.520)

79.560(35.360–450.840)

75.140(29.170–293.490)

70.720(27.400–328.850)

 < 0.001

BUCR

13.931(2.016–48.766)

9.087(2.520–11.107)

12.495(11.112–13.755)

15.451(13.774–17.284)

20.000(17.285–48.766)

 < 0.001

Sex(%)

 < 0.001

 Male

4303(48.8%)

1329(57.4%)

1090(54.2%)

1049(48.5%)

835(35.7%)

 Female

4523(51.2%)

986(42.6%)

920(45.8%)

1116(51.5%)

1501(64.3%)

Age.group(%)

 < 0.001

 < 60 years

5872(66.5%)

1865(80.6%)

1439(71.6%)

1399 (64.6%)

1168 (50.0%)

 60–69 years

1405(15.9%)

252(10.9%)

295(14.7%)

352(16.3%)

506 (21.7%)

 70–79 years

988(11.2%)

145 (6.3%)

191(9.5%)

275(12.7%)

377(16.1%)

 80 + years

561 (6.4%)

52(2.2%)

85(4.2%)

139 (6.4%)

285(12.2%)

Drinking(%)

 < 0.001

 Non-drinker

2658(30.1%)

626 (27.0%)

531(26.4%)

659 (30.4%)

842(36.0%)

 1–5 drinks/month

4266(48.3%)

1133(48.9%)

986(49.1%)

1039(48.0%)

1108(47.4%)

 5–10 drinks/month

695(7.9%)

214 (9.2%)

185(9.2%)

156(7.2%)

140(6.0%)

 10 + drinks/month

1207(13.7%)

342(14.8%)

308(15.3%)

311(14.4%)

246(10.5%)

Smoking(%)

 < 0.001

 Never smoker

4600(52.1%)

1070(46.2%)

1020(50.7%)

1152(53.2%)

1358(58.1%)

 Former smoker

2263(25.6%)

479 (20.7%)

514(25.6%)

593(27.4%)

677(29.0%)

 Current smoker

1963(22.2%)

766 (33.1%)

476(23.7%)

420(19.4%)

301(12.9%)

Education(%)

 < 0.001

 9-11th Grade

1441(16.3%)

424(18.3%)

297(14.8%)

343(15.8%)

377(16.1%)

 High School Grad/GED

2133(24.2%)

560 (24.2%)

484(24.1%)

518(23.9%)

571(24.4%)

 Less Than 9th Grade

1077(12.2%)

204 (8.8%)

201(10.0%)

282(13.0%)

390(16.7%)

 Some College or AA degree

2411(27.3%)

694(30.0%)

600 (29.9%)

573(26.5%)

544(23.3%)

 College Graduate or above

1764(20.0%)

433(18.7%)

428(21.3%)

449(20.7%)

454(19.4%)

Hypertension(%)

 < 0.001

 No

5871(66.5%)

1696(73.3%)

1384(68.9%)

1433(66.2%)

1358(58.1%)

 Yes

2955(33.5%)

619(26.7%)

626(31.1%)

732(33.8%)

978(41.9%)

Diabetes(%)

 < 0.001

 No

7815(88.5%)

2158(93.2%)

1819(90.5%)

1922 (88.8%)

1916(82.0%)

 Yes

1011(11.5%)

157(6.8%)

191(9.5%)

243(11.2%)

420(18.0%)

BMI(%)

0.017

 Overweight

3077(34.9%)

786(34.0%)

706(35.1%)

801 (37.0%)

784(33.6%)

 Obesity

3136(35.5%)

811(35.0%)

717(35.7%)

763 (35.2%)

845(36.2%)

 Normal weight

2474(28.0%)

670(28.9%)

549(27.3%)

583(26.9%)

672(28.8%)

 Underweight

139(1.6%)

48(2.1%)

38(1.9%)

18(0.8%)

35(1.5%)

Martial status(%)

 < 0.001

 With partner

667(7.6%)

230(9.9%)

165(8.2%)

137(6.3%)

135(5.8%)

 Married

4824(54.7%)

1154(49.8%)

1086(54.0%)

1230(56.8%)

1354(58.0%)

 Single

3335(37.8%)

931(40.2%)

759(37.8%)

798(36.9%)

847(36.3%)

OSA(%)

0.583

 No

4300(48.7%)

1136(49.1%)

954(47.5%)

1054(48.7%)

1156(49.5%)

 Yes

4526(51.3%)

1179(50.9%)

1056(52.5%)

1111(51.3%)

1180(50.5%)