Table 1b.
Baseline Characteristics (Phase 3, 1991-93) in 1260 Women Across Categories of Sleep Duration. The Whitehall II Study
| Sleep duration, h |
P valuesa | |||||
|---|---|---|---|---|---|---|
| ≤ 5 | 6 | 7 | 8 | 9+ | ||
| Subjects, no. | 56 | 274 | 583 | 304 | 43 | |
| Age, yb | 51.5 ± 6.0 | 49.9 ± 6.0 | 49.5 ± 5.9 | 49.1 ± 6.3 | 48.9 ± 6.2 | 0.05 |
| Lowest level of employmentc | 19 (33.9) | 83 (30.3) | 162 (27.8) | 77 (25.3) | 15 (34.9) | 0.68 |
| Not married | 30 (53.6) | 128 (46.9) | 222 (38.1) | 93 (30.7) | 13 (30.2) | < 0.001 |
| Current smoking | 12 (21.4) | 50 (18.3) | 83 (14.2) | 33 (10.9) | 2 (4.7) | 0.017 |
| Weekly alcohol consumption, units | 5.7 (7.4) | 5.9 (7.1) | 6.1 (7.2) | 6.7 (7.6) | 5.4 (9.0) | 0.11 |
| SF-36 scores | ||||||
| Mental | 49.9 ± 8.8 | 48.9 ± 10.0 | 50.5 ± 8.7 | 50.6 ± 8.9 | 48.8 ± 10.9 | 0.20 |
| Physical | 47.0 ± 10.6 | 51.1 ± 7.7 | 51.5 ± 7.6 | 50.9 ± 8.0 | 46.3 ± 11.3 | < 0.001 |
| BMI, kg/m2 | 26.0 ± 6.2 | 25.6 ± 4.6 | 24.9 ± 4.4 | 25.3 ± 4.3 | 26.0 ± 5.5 | 0.19 |
| Waist circumference, cm | 76.2 ± 14.3 | 74.9 ± 11.7 | 73.7 ± 11.1 | 74.5 ± 10.6 | 77.6 ± 12.6 | 0.20 |
| Blood pressure, mm Hg | ||||||
| Diastolic | 79.0 ± 8.7 | 75.6 ± 9.0 | 75.9 ± 9.2 | 75.8 ± 8.7 | 77.2 ± 9.5 | 0.08 |
| Systolic | 123.1 ± 12.7 | 115.7 ± 13.0 | 116.4 ± 13.8 | 115.7 ± 12.9 | 117.3 ± 13.8 | 0.002 |
| HDL-cholesterol, mmol/Ld | 1.66 (1.55-1.79) | 1.69 (1.64-1.74) | 1.66 (1.63-1.70) | 1.63 (1.56-1.70) | 1.59 (1.48-1.71) | 0.65 |
| Triglycerides, mmol/Ld | 1.09 (0.96-1.24) | 0.99 (0.94-1.05) | 0.98 (0.94-1.02) | 0.99 (0.93-1.04) | 1.05 (0.93-1.20) | 0.48 |
| Fasting glucose, mmol/Ld | 5.2 (5.0-5.5) | 5.0 (5.0-5.1) | 5.0 (5.0-5.1) | 5.0 (5.0-5.1) | 5.0 (4.9-5.2) | 0.17 |
| Fasting Insulin, mmol/Ld | 5.9 (4.7-7.4) | 4.4 (4.1-4.9) | 4.6 (4.4-4.9) | 4.8 (4.4-5.3) | 5.4 (4.3-6.8) | 0.31 |
| IL-6, pg/mLd | 1.79 (1.43-2.20) | 1.62 (1.51-1.74) | 1.62 (1.54-1.71) | 1.48 (1.39-1.58) | 2.02 (1.62-2.54) | 0.08 |
| hs-CRP, mg/Ld | 1.46 (1.03-2.05) | 0.97 (0.84-1.12) | 0.88 (0.80-0.97) | 0.96 (0.83-1.10) | 1.37 (0.96-1.95) | 0.020 |
Data are expressed as the mean ± SD or as number (percentage) unless otherwise indicated.
BMI refers to body mass index; HDL, high-density lipoprotein; IL-6, interleukin-6; hs-CRP, high-sensitivity C reactive protein.
a
P Value for comparison across sleep duration groups using the χ2 analysis for categorical variables and Kruskal-Wallis test for continuous variables.
b
Age ranges from 39-61 years (median: 49).
c
Clerical/support.
d
Data are presented as geometric mean (95% confidence interval).