Age-adjusted characteristics of the study population at 2001 baseline by sleep duration
| Variables | ||||
|---|---|---|---|---|
| Amount of sleep over a 24-hour period (hours) | ≤6 | 7 | 8 | >9 |
| Proportion of sample (%) | 29 | 43 | 23 | 5 |
| Age, years* | 46.92±4.57 | 46.66±4.66 | 46.61±4.70 | 46.44±4.68 |
| Body mass index, kg/m2 | 26.62±5.29 | 25.89±4.96 | 25.77±4.91 | 26.39±5.24 |
| Physical activity, MET-hours/week† | 19.69±22.89 | 19.88±21.64 | 20.35±22.23 | 16.83±20.83 |
| Alcohol intake, g/day | 3.57±6.86 | 4.01±6.84 | 4.35±7.70 | 4.33±8.66 |
| Alternate Health Eating Index‡ | 47.18±10.68 | 47.91±10.62 | 48.23±10.82 | 47.49±11.06 |
| Rotating night shift work, ≥10 years, % | 12 | 7 | 6 | 7 |
| First-degree relative history of melanoma, % | 12 | 11 | 11 | 13 |
| Red or blonde hair, % | 19 | 20 | 20 | 21 |
| Moles, ≥10 on lower legs, % | 14 | 15 | 15 | 15 |
| Artificial tanning, ≥6 times/year at ages 25–35, % | 3 | 3 | 3 | 3 |
| Time spent in sun, ≥5 hours/week at ages 25–35, % | 43 | 44 | 44 | 45 |
| Severe sunburns, ≥6 at ages 15–20, % | 10 | 10 | 10 | 11 |
| Skin sensitivity to burning,§ % | 41 | 42 | 40 | 42 |
| Annual UV-B flux at residence, ≥145 R-B units,¶ % | 20 | 22 | 24 | 26 |
| Sleep not usually adequate, % | 81 | 48 | 18 | 21 |
| Sleepy ≥4 days/week, % | 18 | 10 | 8 | 21 |
| Snore most nights, % | 17 | 15 | 15 | 20 |
| Restless legs syndrome | 3 | 2 | 2 | 4 |
| Current smoker, % | 11 | 8 | 7 | 8 |
| Married, % | 75 | 81 | 83 | 78 |
| In top 20 per cent of economic ladder,** % | 8 | 12 | 14 | 13 |
| Oral contraceptive use, ≥8 years, % | 23 | 22 | 21 | 22 |
| Current use of postmenopausal hormones,†† % | 60 | 66 | 65 | 69 |
Values are means±SD or percentages and are standardised to the age distribution of the study population.
*Value is not age-adjusted.
†Metabolic equivalents from recreational and leisure-time activities.
‡Score of 0–100 measuring adherence to a dietary pattern most predictive of disease risk.
§Skin reaction after two or more hours in the sun without sunscreen on a bright sunny day during childhood and adolescence.
¶Measured in Robertson-Berger units (count×10−4).
**Self-reported economic status compared to others.
††Calculated among postmenopausal women only.
MET, metabolic equivalent.