Table 1. Baseline characteristics of the participants according to sleep duration.
|
Sleep duration (hours per day)
|
||||
|---|---|---|---|---|
| ⩽6 | 7 | 8 | ⩾9 | |
| Number of participants | 4549 | 7087 | 8667 | 3692 |
| Mean age (years), s.d.a | 58.8 (10.5) | 58.3 (10.0) | 61.4 (9.3) | 66.4 (8.7) |
| Mean body mass index (kg m−2), s.d.a | 23.6 (3.3) | 23.7 (3.3) | 23.8 (3.4) | 24.0 (3.9) |
| Mean total caloric intake (kcal day−1), s.d.a | 1220.2 (378.8) | 1263.0 (367.7) | 1242.1 (380.0) | 1171.8 (410.6) |
| History of diseases (%) b | ||||
| Presence | 29.9 | 28.7 | 34.2 | 44.2 |
| Absence | 70.1 | 71.3 | 65.8 | 55.8 |
| Family history of cancer in first-degree relatives (%) | ||||
| Presence | 35.0 | 33.1 | 31.1 | 29.7 |
| Absence | 65.0 | 66.9 | 68.9 | 70.3 |
| Job (%) | ||||
| Employed | 35.2 | 38.8 | 32.6 | 23.5 |
| Unemployed | 38.0 | 36.1 | 39.5 | 43.6 |
| Marital status (%) | ||||
| Married | 66.0 | 70.5 | 66.8 | 54.8 |
| Unmarried | 23.8 | 18.9 | 20.0 | 27.3 |
| Education (%) | ||||
| Junior high school or less | 46.9 | 46.8 | 57.6 | 66.3 |
| High school | 36.8 | 39.0 | 29.6 | 18.2 |
| College/university or higher | 10.4 | 9.0 | 6.2 | 3.4 |
| Cigarette smoking (%) | ||||
| Never smoker | 69.1 | 72.2 | 68.9 | 65.3 |
| Ex-smoker | 2.7 | 1.8 | 1.8 | 2.2 |
| Current smoker (<20 cigarettes per day) | 5.7 | 4.2 | 3.3 | 2.8 |
| Current smoker (⩾20 cigarettes per day) | 3.2 | 2.1 | 1.4 | 1.1 |
| Alcohol consumption (%) | ||||
| Never drinker | 54.7 | 60.0 | 60.2 | 60.3 |
| Ex-drinker | 4.7 | 3.3 | 3.1 | 4.1 |
| Current drinker | 25.3 | 21.0 | 16.2 | 12.1 |
| Walking status (%) | ||||
| Longer than 1 h per day | 38.5 | 39.7 | 38.6 | 36.0 |
| Less than 1 h per day | 52.3 | 51.5 | 51.2 | 51.3 |
| Menopausal status (%) | ||||
| Premenopausal | 23.7 | 23.5 | 13.9 | 5.7 |
| Postmenopausal | 62.5 | 62.5 | 68.2 | 68.1 |
| Age at menarche (%) | ||||
| ⩽13 years | 7.0 | 7.4 | 6.3 | 5.4 |
| 14–5 years | 19.5 | 20.5 | 20.7 | 17.0 |
| ⩾16 years | 18.1 | 16.7 | 19.6 | 22.2 |
| Age at first delivery (%) | ||||
| ⩽21 years | 16.3 | 16.0 | 18.3 | 20.6 |
| 22–5 years | 48.4 | 52.1 | 50.6 | 45.2 |
| ⩾26 years | 20.6 | 18.8 | 16.1 | 13.1 |
| Number of deliveries (%) | ||||
| 0 births | 3.1 | 2.7 | 2.8 | 3.0 |
| 1– births | 39.3 | 40.0 | 35.3 | 22.4 |
| ⩾3 births | 43.6 | 45.4 | 47.2 | 52.7 |
| Using of oral contraceptive drugs (%) | ||||
| Yes | 5.1 | 4.4 | 3.1 | 2.5 |
| No | 81.0 | 82.5 | 79.2 | 72.9 |
| Using of hormone drugs except for oral contraceptive drugs (%) | ||||
| Yes | 8.1 | 6.8 | 6.3 | 5.7 |
| No | 77.9 | 79.7 | 76.4 | 69.3 |
a
standard deviation.
b
History of stroke, hypertension, myocardial infarction, or diabetes mellitus.