Table 1.
General characteristics of participants according to sleep duration.
| Sleep duration (hours a day) | |||||||
|---|---|---|---|---|---|---|---|
| ≤5 | 6 | 7 | 8 | ≥9 | Total | p value | |
| N(%) | 1,108 (13.0) | 2,048 (24.1) | 2,597 (30.5) | 2,082 (24.5) | 670 (7.9) | 8505 (100) | |
| Mean age (years) | 51.3 ± 14.6 | 43.8 ± 12.8 | 42.5 ± 12.7 | 41.1 ± 12.6 | 38.8 ± 14.3 | 43.3 ± 13.5 | <0.01 |
| Education | <0.01 | ||||||
| ≥college | 181 (16.3) | 631 (30.8) | 887 (34.2) | 734 (35.3) | 198 (29.6) | 2631 (30.9) | |
| Middle/high school | 486 (43.9) | 1022 (49.9) | 1285 (49.5) | 1027 (49.3) | 339 (50.6) | 4159 (48.9) | |
| ≤elementary school | 441 (39.8) | 395 (19.3) | 425 (16.4) | 321 (15.4) | 133 (19.9) | 1715 (20.2) | |
| Monthly income (dollars) | <0.01 | ||||||
| ≥3,010 | 296 (26.7) | 878 (42.9) | 1107 (42.6) | 873 (41.9) | 241 (36.0) | 3395 (40.0) | |
| 1,010–3,000 | 457 (41.3) | 843 (41.2) | 1087 (41.9) | 903 (43.4) | 303 (45.2) | 2866 (42.6) | |
| ≤1,000 | 355 (32.0) | 327 (16.0) | 403 (15.5) | 306 (14.7) | 126 (18.8) | 1517 (17.8) | |
| Smoking | <0.01 | ||||||
| Nonsmoker | 978 (88.3) | 1883 (91.9) | 2375 (91.5) | 1872 (89.9) | 562 (83.9) | 7670 (90.2) | |
| Past-smoker | 44 (4.0) | 67 (3.3) | 106 (4.1) | 95 (4.6) | 48 (7.2) | 360 (4.2) | |
| Current smoker | 86 (7.8) | 98 (4.8) | 116 (4.5) | 115 (5.5) | 60 (9.0) | 475 (5.6) | |
| High risk drinking | <0.01 | ||||||
| Never | 449 (50.2) | 607 (29.6) | 734 (28.3) | 570 (27.4) | 203 (30.3) | 5131 (60.3) | |
| ≤once a month | 347 (31.3) | 746 (36.4) | 957 (36.9) | 765 (36.7) | 209 (31.2) | 2600 (30.6) | |
| ≥once a week | 312 (28.2) | 695 (33.9) | 906 (34.9) | 747 (35.9) | 258 (38.5) | 774 (9.1) | |
| Physical activity (METs/week) | 3359.8 ± 5467.4 | 2748.7 ± 4030.1 | 2600.5 ± 4058.9 | 2567.3 ± 4042.7 | 2234.9 ± 3898.6 | 2695.5 ± 4250.1 | <0.01 |
| Intense physical activity (METs/week) | 1305.7 ± 4132.6 | 838.6 ± 2274.0 | 827.0 ± 2593.0 | 814.1 ± 2479.1 | 501.1 ± 1577.7 | 861.8 ± 2688.3 | <0.01 |
| BMI (kg/m 2) | 23.5 ± 3.3 | 23.0 ± 3.3 | 22.8 ± 3.2 | 22.7 ± 3.4 | 22.4 ± 3.6 | 22.9 ± 3.3 | <0.01 |
| 24 h recall-total calories (kcal) | 1588.3 ± 635.9 | 1653.5 ± 662.6 | 1678.8 ± 580.2 | 1701.6 ± 636.1 | 1744.4 ± 669.8 | 1672.2 ± 629.9 | <0.01 |
| Metabolic syndrome | <0.01 | ||||||
| Yes | 240 (21.7) | 308 (15.0) | 396 (15.3) | 288 (13.8) | 106 (15.8) | 1338 (15.7) | |
| No | 868 (78.3) | 1740 (85.0) | 2201 (84.8) | 1794 (86.2) | 564 (84.2) | 7167 (84.3) | |
| HDL cholesterol (mg/dl) | 50.9 ± 11.1 | 51.8 ± 10.8 | 51.2 ± 10.5 | 51.1 ± 10.8 | 51.0 ± 10.8 | 51.3. ± 10.7 | 0.17 |
| Triglycerides (mg/dl) | 111.7 ± 69.0 | 101.0 ± 65.7 | 100.0 ± 69.5 | 100.0 ± 65.8 | 103.9 ± 66.6 | 102.1 ± 67.5 | 0.02 |
| Waist circumference (cm) | 79.1 ± 9.4 | 77.3 ± 9.3 | 76.4 ± 8.9 | 76.4 ± 9.3 | 75.7 ± 9.9 | 76.9 ± 9.3 | 0.01 |
| Fasting glucose (mg/dl) | 92.6 ± 15.0 | 91.5 ± 13.3 | 91.1 ± 11.2 | 91.6 ± 12.6 | 90.8 ± 11.2 | 91.5 ± 12.6 | <0.01 |
| SBP (mmHg) | 115.3 ± 17.2 | 110.3 ± 14.7 | 109.7 ± 15.5 | 109.3 ± 14.6 | 108.7 ± 14.7 | 110.4 ± 15.4 | <0.01 |
| DBP (mmHg) | 73.7 ± 10.0 | 72.0 ± 9.4 | 71.4 ± 9.9 | 71.2 ± 9.5 | 70.6 ± 9.4 | 71.7 ± 9.7 | 0.02 |
METs, metabolic equivalent; SBP, systolic blood pressure; DBP, diastolic blood pressure; HDL, high density lipoprotein; BMI, body mass index; data are mean + SD or number and percentages. p value is calculated from analysis of variance for continuous variables and chi-square test for categorical variables, respectively.