TABLE 1.
Baseline sample characteristics according to sleep categories.
| Variable | Total | Nighttime sleep duration |
Daytime napping |
Total sleep duration |
|||||||||
| ≤6 h | 6 to ≤8 h | >8 h | P-value | 0 | 1 to ≤60 min | >60 min | P-value | <7 h | 7 to ≤9 h | >9 h | P-value | ||
| n = 14,532 | n = 6,685 | n = 6,528 | n = 1,319 | n = 6,656 | n = 5,342 | n = 2,508 | n = 5,121 | n = 7,629 | n = 1,782 | ||||
| Demographic characteristics | |||||||||||||
| Age, years, mean (SD) | 59.83 (9.49) | 60.43 (9.39) | 58.99 (9.31) | 60.92 (10.43) | < 0.0001 | 59.25 (9.18) | 60.00 (9.60) | 60.98 (9.88) | < 0.0001 | 60.32 (9.31) | 59.23 (9.36) | 60.97 (10.31) | < 0.0001 |
| Male, n (%) | 7,052 (48.53) | 3,158 (47.24) | 3,265 (50.02) | 629 (47.69) | 0.005 | 2,790 (41.92) | 2,801 (52.43) | 1,448 (57.74) | < 0.0001 | 2,217 (43.29) | 3,893 (51.03) | 942 (52.86) | < 0.0001 |
| Education level (missing = 4) | < 0.0001 | <0.0001 | < 0.0001 | ||||||||||
| Elementary school or below, n (%) | 6,264 (43.1) | 2,992 (44.76) | 2,592 (39.72) | 680 (51.55) | 3,150 (47.34) | 2,073 (38.82) | 1,029 (41.03) | 2,445 (47.74) | 3,001 (39.36) | 818 (45.90) | |||
| From Middle school to Bachelor’s degree, n (%) | 7,878 (54.21) | 3,536 (52.90) | 3,717 (56.97) | 625 (47.38) | 3,399 (51.08) | 3,032 (56.78) | 1,434 (57.18) | 2,572 (50.22) | 4,363 (57.22) | 943 (52.92) | |||
| Bachelor’s degree or beyond, n (%) | 386 (2.66) | 156 (2.33) | 216 (3.31) | 14 (1.06) | 105 (1.58) | 235 (4.40) | 45 (1.79) | 104 (2.03) | 2,61 (3.42) | 21 (1.18) | |||
| Married, n (%) | 12,859 (88.49) | 5,859 (87.64) | 5,867 (89.87) | 1,133 (85.90) | < 0.0001 | 5,840 (87.74) | 4,769 (89.27) | 2,227 (88.80) | 0.0284 | 4,462 (87.13) | 6,834 (89.58) | 1,563 (87.71) | 0.0001 |
| Rural, n (%) | 12,886 (88.67) | 5,930 (88.72) | 5,729 (87.77) | 1,227 (93.10) | < 0.0001 | 5,937 (89.22) | 4,648 (87.02) | 2,279 (90.87) | < 0.0001 | 4,548 (88.83) | 6,696 (87.78) | 1,642 (92.20) | < 0.0001 |
| Lifestyle factors | |||||||||||||
| Smoking status (missing = 5) | 0.3257 | < 0.0001 | <0.0001 | ||||||||||
| Never, n (%) | 8,767 (60.33) | 4,049 (60.58) | 3,895 (59.70) | 823 (62.40) | 4,286 (64.42) | 3,157 (59.11) | 1,309 (52.21) | 3,227 (63.03) | 4,519 (59.26) | 1,021 (57.33) | |||
| Quit, n (%) | 1,292 (8.89) | 592 (8.86) | 580 (8.89) | 120 (9.10) | 462 (6.94) | 564 (10.56) | 261 (10.41) | 432 (8.44) | 675 (8.85) | 185 (10.39) | |||
| Current, n (%) | 4,468 (30.75) | 2,043 (30.57) | 2,049 (31.41) | 376 (28.51) | 1,905 (28.63) | 1,620 (30.33) | 937 (37.38) | 1,461 (28.54) | 2,432 (31.89) | 575 (32.29) | |||
| Drinking status (missing = 3,641) | 0.0873 | < 0.0001 | 0.0585 | ||||||||||
| Never, n (%) | 8,541 (58.77) | 3,904 (77.82) | 3,835 (79.12) | 802 (78.09) | 4,239 (81.68) | 2,996 (75.89) | 1,289 (74.42) | 3,111 (79.12) | 4,427 (78.41) | 1,003 (76.39) | |||
| Quit, n (%) | 1,167 (8.03) | 556 (11.08) | 484 (9.99) | 127 (12.37) | 472 (9.09) | 463 (11.73) | 230 (13.28) | 410 (10.43) | 587 (10.40) | 170 (12.95) | |||
| Current, n (%) | 1,183 (8.14) | 557 (11.10) | 528 (10.89) | 98 (9.54) | 479 (9.23) | 489 (12.39) | 213 (12.30) | 411 (10.45) | 632 (11.19) | 140 (10.66) | |||
| Physical activity (missing = 2,360) | 0.4266 | 0.0069 | 0.1229 | ||||||||||
| Walking, n (%) | 10,508 (72.31) | 4,819 (72.09) | 4,707 (72.10) | 982 (74.45) | 4,748 (71.33) | 3,868 (72.41) | 1,870 (74.56) | 3,662 (71.51) | 5,521 (72.37) | 1,325 (74.35) | |||
| Moderate, n (%) | 1,873 (12.89) | 875 (13.09) | 837 (12.82) | 161 (12.21) | 856 (12.86) | 704 (13.18) | 313 (12.48) | 692 (13.51) | 960 (12.58) | 221 (12.40) | |||
| Vigorous, n (%) | 2,151 (14.8) | 991 (14.82) | 984 (15.07) | 176 (13.34) | 1,052 (15.81) | 770 (14.41) | 325 (12.96) | 767 (14.98) | 1,148 (15.05) | 236 (13.24) | |||
| Mean nighttime sleep duration, h | 6.69 (1.57) | 5.30 (0.78) | 7.52 (0.50) | 9.68 (0.84) | < 0.0001 | 6.59 (1.59) | 6.67 (1.47) | 7.04 (1.66) | < 0.0001 | 5.13 (0.79) | 7.19 (0.88) | 9.05 (1.17) | < 0.0001 |
| Mean total sleep duration, h | 7.35 (1.81) | 5.88 (1.08) | 8.22 (0.92) | 10.46 (1.27) | < 0.0001 | 6.59 (1.59) | 7.51 (1.51) | 9.01 (1.73) | < 0.0001 | 5.44 (0.78) | 7.89 (0.74) | 10.50 (0.99) | |
| Mean daytime napping, min | 39.21 (44.75) | 34.94 (42.33) | 42.05 (45.34) | 46.79 (51.24) | < 0.0001 | 0.00 (0.00) | 50.94 (14.51) | 118.26 (22.65) | < 0.0001 | 18.67 (29.76) | 41.86 (42.08) | 86.80 (51.98) | < 0.0001 |
| Clinical/biochemical measures | |||||||||||||
| BMI ≥ 25, n (%) | 3,810 (26.22) | 1,679 (25.12) | 1,826 (27.97) | 305 (23.12) | < 0.0001 | 1,550 (23.29) | 1,511 (28.29) | 740 (29.51) | < 0.0001 | 1,218 (23.78) | 2,107 (27.62) | 485 (27.22) | < 0.0001 |
| Elevated waist circumference, n (%) | 6,213 (42.75) | 2,816 (50.12) | 2,829 (51.61) | 568 (51.87) | 0.2338 | 2,785 (50.13) | 2,300 (51.51) | 1,117 (51.83) | 0.2535 | 2,146 (50.41) | 3,269 (50.86) | 798 (52.85) | 0.2601 |
| Elevated blood pressure, n (%) | 6,422 (44.19) | 2,945 (44.07) | 2,898 (44.41) | 579 (43.93) | 0.9049 | 2,863 (43.03) | 2,346 (43.93) | 1,203 (47.99) | 0.0001 | 2,213 (43.23) | 3,383 (44.36) | 826 (46.38) | 0.0656 |
| Elevated triglycerides, n (%) | 3,140 (21.61) | 1,415 (21.29) | 1,441 (22.21) | 284 (21.60) | 0.4442 | 1,330 (20.09) | 1,226 (23.06) | 578 (23.24) | 0.0001 | 1,063 (20.88) | 1,668 (21.98) | 409 (23.09) | 0.1129 |
| Reduced HDL-C, n (%) | 4,402 (30.29) | 2,002 (30.13) | 1,989 (30.65) | 411 (31.25) | 0.6553 | 1,942 (29.33) | 1,658 (31.19) | 795 (31.97) | 0.0185 | 1,526 (29.98) | 2,313 (30.48) | 563 (31.79) | 0.3619 |
| Elevated fasting glucose, n (%) | 5,470 (37.64) | 2,574 (54.01) | 2,424 (52.15) | 472 (50.70) | 0.0743 | 2,436 (52.04) | 2,078 (53.57) | 947 (53.62) | 0.2924 | 1,965 (53.84) | 2,843 (52.37) | 662 (52.29) | 0.3521 |
| Metabolic syndrome, n (%) | 4,094 (28.17) | 1,845 (27.60) | 1,880 (28.80) | 369 (27.98) | 0.3046 | 1,748 (26.26) | 1,585 (29.67) | 755 (30.10) | < 0.0001 | 1,384 (27.03) | 2,192 (28.73) | 518 (29.07) | 0.0737 |
| Clinical characteristics | |||||||||||||
| Health state (missing = 1) | < 0.0001 | 0.0617 | < 0.0001 | ||||||||||
| Good, n (%) | 504 (4.54) | 169 (3.17) | 287 (6.01) | 48 (4.86) | 232 (4.55) | 181 (4.46) | 91 (4.74) | 126 (3.06) | 304 (5.38) | 74 (5.58) | |||
| Fair, n (%) | 6,964 (62.74) | 3,220 (60.31) | 3,132 (65.61) | 612 (62.01) | 3,140 (61.54) | 2,618 (64.47) | 1,195 (62.30) | 2,426 (58.87) | 3,726 (65.90) | 812 (61.28) | |||
| Poor, n (%) | 3,632 (32.72) | 1,950 (36.52) | 1,355 (28.38) | 327 (33.13) | 1,730 (33.91) | 1,262 (31.08) | 632 (32.95) | 1,569 (38.07) | 1,624 (28.72) | 439 (33.13) | |||
| History of stroke, n (%) (missing = 112) | 356 (2.44) | 180 (2.70) | 142 (2.18) | 39 (2.96) | 0.0835 | 150 (2.26) | 136 (2.55) | 74 (2.96) | 0.1449 | 148 (2.89) | 155 (2.04) | 58 (3.26) | 0.0008 |
| History of heart problems, n (%) (missing = 74) | 1,723 (11.86) | 912 (13.72) | 690 (10.62) | 121 (9.23) | < 0.0001 | 709 (10.69) | 716 (13.48) | 294 (11.81) | < 0.0001 | 718 (14.09) | 820 (10.80) | 185 (10.45) | < 0.0001 |
| History of cancer, n (%) (missing = 62) | 144 (0.99) | 83 (1.25) | 49 (0.75) | 12 (0.91) | 0.016 | 64 (0.96) | 58 (1.09) | 22 (0.88) | 0.6373 | 63 (1.24) | 66 (0.87) | 15 (0.85) | 0.0979 |
| History of disabilities, n (%) | 2,358 (16.23) | 1,125 (16.83) | 952 (14.58) | 281 (21.30) | < 0.0001 | 1,015 (15.25) | 863 (16.15) | 474 (18.90) | 0.0001 | 849 (16.58) | 1,158 (15.18) | 351 (19.70) | < 0.0001 |
| History of psychiatric problem, n (%) (missing = 57) | 149 (1.03) | 82 (1.23) | 55 (0.85) | 12 (0.91) | 0.0827 | 60 (0.90) | 55 (1.03) | 34 (1.36) | 0.1532 | 67 (1.31) | 61 (0.80) | 21 (1.19) | 0.0157 |
| History of memory related disease (missing = 43) | 185 (1.27) | 95 (1.42) | 66 (1.01) | 24 (1.83) | 0.0194 | 75 (1.13) | 67 (1.26) | 43 (1.72) | 0.0811 | 67 (1.31) | 86 (1.13) | 32 (1.80) | 0.0726 |
Data are % for categorical variables and mean (SD) for continuous variables.
P-values were derived from analysis of variance or Mann-Whitney U tests for continuous variables according to data distribution and χ2 tests for category variable.
BMI, body mass index; HDL-C, high-density lipoprotein cholesterol.