Table 2 Characteristics of the 3,698 middle-aged birth cohort participants according to the quartiles of time in bed regularity (standard deviations of accelerometer-measured time in bed over seven days)
| Â | Time in bed regularity (hh:mm:ss) | Â | |||
|---|---|---|---|---|---|
|  | Q1  ≤ 0:54:55 | Q2 0:54:56–1:16:12 | Q3 1:16:13–1:43:17 | Q4  ≥ 01:43:18 |  p-value |
n (total = 3698) | 925 | 924 | 925 | 924 |  |
Factors related to sleep and time in bed | |||||
Bedtime (hh:mm) | 23:10 (1:02) | 23:13 (1:01) | 23:20 (1:09) | 23:40 (1:34) |  < 0.001 |
Wake-up time (hh:mm) | 7:07 (1:01) | 7:11 (1:02) | 7:17 (1:05) | 7:34 (1:25) |  < 0.001 |
Time in bed (hh:mm) | 7:56 (0:50) | 7:58 (0:54) | 7:58 (0:59) | 7:54 (1:10) | 0.198 |
Chronotype (n [%]) |  < 0.001 | ||||
 Morning-type | 409 (46) | 390 (44.7) | 335 (38.2) | 331 (38.3) |  < 0.05 |
 Day-type | 444 (49.9) | 452 (58) | 497 (56.7) | 449 (51.9) |  < 0.05 |
 Evening-type | 37 (4.2) | 31 (3.6) | 45 (5.1) | 85 (9.8) |  < 0.05 |
Work schedule (n [%]) |  |  |  |  |  < 0.001 |
 Day work | 698 (75.5) | 650 (70.3) | 591 (52.8) | 488 (52.8) |  < 0.05 |
 Shift work | 89 (9.6) | 119 (12.9) | 156 (16.9) | 245 (26.5) |  < 0.05 |
 Not working/no information available | 138 (14.9) | 155 (16.8) | 178 (19.2) | 191 (20.7) |  < 0.05 |
Sociodemographic and lifestyle factors | |||||
Men (n [%]) | 343 (37.2) | 364 (39.6) | 331 (35.8) | 411 (44.6) | 0.001 |
High education (n [%]) | 286 (32.6) | 257 (30.3) | 242 (28.0) | 212 (24.7) | 0.002 |
Current smoker (n [%]) | 125 (14) | 131 (15) | 163 (18.5) | 201 (23.1) |  < 0.001 |
Heavy alcohol drinkers* (n [%]) | 55 (5.9) | 56 (6.1) | 67 (7.2) | 96 (10.4 | 0.001 |
Total PA (MET min/day) | 1153.4 (353.3) | 1097.5 (327.0) | 1081.0 (315.5) | 1015.5 (923.0) |  < 0.001 |
Sedentary time (min) | 571.7 (90.7) | 578.9 (88.7) | 575.5 (87.6) | 582.0 (91.3) | 0.131 |
Cardiometabolic health markers | |||||
WC (cm) | 89.2 (12.9) | 90.0 (13.3) | 91.0 (13.8) | 92.6 (13.8) |  < 0.001 |
 Men | 95.0 (11.4) | 95.8 (11.4) | 98.0 (12,6) | 98.1 (12.5) | 0.058 |
 Women | 85,2 (12.1) | 86.2 (13.1) | 87.2 (12.9) | 88.2 (13.3) |  < 0.001 |
BMI (kg/m2) | 26 (4.7) | 26.4 (4.8) | 27 (5) | 27.2 (5) |  < 0.001 |
SBP (mmHg) | 123.2 (15.7) | 125.2 (15.2) | 125 (15.6) | 125.6 (16.3) | 0.010 |
DBP (mmHg) | 83 (10.5) | 84.3 (10.2) | 84.8 (10.4) | 85.2 (10.9) |  < 0.001 |
Body fat (%) | 28.4 (9.0) | 28.8 (9.4) | 29.96 (9.3) | 29.4 (9.5) | 0.003 |
Fat mass (kg) | 22.0 (10.0) | 22.6 (10.8) | 23.8 (11.3) | 23.8 (11.2) | 0.001 |
Visceral fat area (cm2) | 100.0 (40.1) | 102.4 (40.4) | 107.2 (43.2) | 108.2 (42.7) |  < 0.001 |
Fasting insulin (pmol/L) | 9.15 (6.56) | 9.04 (5.91) | 9.96 (10.4) | 10.26 (8.68) | 0.007 |
2-h insulin (pmol/L) | 57.07 (53.03) | 58.06 (55.33) | 63.93 (66.29) | 64.32 (60) | 0.027 |
Fasting glucose (mmol/L) | 5.43 (0.7) | 5.46 (0.8) | 5.49 (0.84) | 5.52 (0.64) | 0.003 |
2-h glucose (mmol/L) | 5.76 (1.64) | 5.74 (1.63) | 5.88 (1.58) | 5.96 (1.8) | 0.019 |
Triglycerides (mmol/L) | 1.14 (0.69) | 1.16 (0.7) | 1.25 (0.9) | 1.28 (0.81) |  < 0.001 |
Total HDL cholesterol ratio | 3.51 (0.98) | 3.57 (1.06) | 3.64 (1.02) | 3.61 (1.03) | 0.036 |
LDL/HDL cholesterol ratio | 2.29 (0.9) | 2.34 (0.96) | 2.41 (0.93) | 2.37 (0.92) | 0.033 |