Table 1.
Baseline characteristics of study participants. *
| Midday Group (Reference) (n=27,803) |
Early Morning Group (n=18,477) |
Late Morning Group (n= 25,700) |
Night Group (n= 22,509) |
P-value | |
|---|---|---|---|---|---|
| Sociodemographic Variables | |||||
| Age at Recruitment (years) | 57.9 (7.0) | 53.6 (7.9) | 59.1 (6.9) | 52.7 (7.8) | <0.001 |
| Female | 15,506 (55.8) | 10,096 (54.6) | 14,877 (57.9) | 12,721 (56.5) | <0.001 |
| Race/Ethnicity | |||||
| White | 25,831 (93.2) | 16,837 (91.4) | 24,201 (94.5) | 20,067 (89.5) | <0.001 |
| Black | 82 (0.3) | 105 (0.6) | 48 (0.2) | 115 (0.5) | |
| Asian | 921 (3.3) | 805 (4.4) | 719 (2.8) | 1,239 (5.5) | |
| Mixed | 757 (2.7) | 564 (3.1) | 552 (2.2) | 807 (3.6) | |
| Other | 115 (0.4) | 101 (0.5) | 96 (0.4) | 197 (0.9) | |
| Employment | |||||
| Employed | 14,924 (54.1) | 14,106 (76.8) | 11,855 (46.5) | 17,381 (77.7) | <0.001 |
| Retired | 10,670 (38.7) | 3,358 (18.3) | 12,004 (47.1) | 3,471 (15.5) | |
| Unemployed | 2,004 (7.3) | 904 (4.9) | 1,646 (6.5) | 1,525 (6.8) | |
| Townsend Deprivation Index | |||||
| 1st quartile, least deprived | 7,190 (25.9) | 4,165 (22.6) | 7,102 (27.7) | 5,084 (22.6) | <0.001 |
| 2nd quartile | 7,088 (25.5) | 4,389 (23.8) | 6,887 (26.8) | 5,213 (23.2) | |
| 3rd quartile | 6,922 (24.9) | 4,750 (25.8) | 6,395 (24.9) | 5,527 (24.6) | |
| 4th quartile | 6,557 (23.6) | 5,133 (27.8) | 5,270 (20.5) | 6,640 (29.6) | |
| Lifestyle Factors | |||||
| Body-Mass Index (kg/m2) | |||||
| < 18.5 | 130 (0.5) | 126 (0.7) | 146 (0.6) | 134 (0.6) | <0.001 |
| 18.5-24.9 | 10,072 (36.3) | 7,252 (39.3) | 9,974 (38.9) | 9,279 (41.4) | |
| 25-29.9 | 11,868 (42.8) | 7,396 (40.1) | 10,944 (42.7) | 8,612 (38.4) | |
| ≥ 30 | 5,672 (20.4) | 3,663 (19.9) | 4,590 (17.9) | 4,414 (19.7) | |
| Healthy Eating Score | 3.3 (0.9) | 3.3 (1.0) | 3.4 (0.9) | 3.2 (0.9) | <0.001 |
| Tobacco Use | |||||
| Never | 14,982 (54.0) | 10,967 (59.5) | 14,503 (56.6) | 13,388 (59.6) | <0.001 |
| Previous | 10,553 (38.1) | 6,279 (34.1) | 9,816 (38.3) | 7,243 (32.3) | |
| Current | 2,195 (7.9) | 1,185 (6.4) | 1,302 (5.1) | 1,822 (8.1) | |
| Alcohol Intake | |||||
| Never | 658 (2.4) | 622 (3.4) | 758 (3.0) | 717 (3.2) | <0.001 |
| Previous | 695 (2.5) | 594 (3.2) | 668 (2.6) | 626 (2.8) | |
| Current | 26,430 (95.1) | 17,244 (93.4) | 24,248 (94.4) | 21,142 (94.0) | |
| Sleep Duration (hours) | |||||
| ≤ 6 | 5,473 (19.7) | 4,823 (26.2) | 5,172 (20.2) | 5,231 (23.3) | <0.001 |
| 7-8 | 19,937 (71.9) | 12,901 (70.0) | 18,603 (72.6) | 16,127 (71.9) | |
| ≥9 | 2,313 (8.3) | 711 (3.9) | 1,839 (7.2) | 1,083 (4.8) | |
| Other Risk Factors and Chronic Conditions | |||||
| Family History of CVD | 16,683 (60.0) | 9,956 (53.9) | 15,452 (60.1) | 11,992 (53.3) | <0.001 |
| Hypertension | 21,572 (77.7) | 13,252 (71.8) | 20,249 (78.9) | 15,536 (69.1) | <0.001 |
| High Cholesterol | 10,521 (40.0) | 5,504 (31.5) | 9,944 (40.9) | 6,901 (32.5) | |
| Heart Attack | 694 (2.5) | 292 (1.6) | 692 (2.7) | 316 (1.4) | <0.001 |
| Angina | 1,207 (4.3) | 542 (2.9) | 1,154 (4.5) | 614 (2.7) | <0.001 |
| Stroke | 449 (1.6) | 210 (1.1) | 426 (1.7) | 248 (1.1) | <0.001 |
| Diabetes | 1,187 (4.3) | 702 (3.8) | 969 (3.8) | 844 (3.8) | <0.001 |
| Long-Standing Illness | 8,602 (31.6) | 4,650 (25.6) | 7,310 (29.0) | 5,933 (26.9) | <0.001 |
| General Health Status | |||||
| Excellent | 5,492 (19.8) | 4,242 (23.0) | 5,592 (21.8) | 5,181 (23.1) | <0.001 |
| Good | 16,693 (60.1) | 11,017 (59.8) | 15,763 (61.5) | 13,056 (58.2) | |
| Fair | 4,719 (17.0) | 2,809 (15.2) | 3,730 (14.6) | 3,536 (15.8) | |
| Poor | 8,49 (3.1) | 364 (2.0) | 548 (2.1) | 669 (3.0) | |
| Accelerometer Parameters | |||||
| Mean Acceleration | 26.1 (21.6 - 31.3) | 28.3 (23.6 - 33.8) | 26.5 (22.0 - 31.9) | 27.8 (23.0 - 33.3) | <0.001 |
*
Data are mean (SD) for normally distributed variables, median (interquartile range) for non-normally distributed variables, and number (percent) for categorical variables.