Sleep duration and the risk of breast cancer: the Ohsaki Cohort
Study
M Kakizaki, S Kuriyama, T Sone, K Ohmori-Matsuda,
A Hozawa, N Nakaya, S Fukudo and I Tsuji
|
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.
|
