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

 

 

Table 1. Baseline characteristics of the participants according to sleep duration

 

Sleep duration (hours per day)

 

less than or equal to6

7

8

greater than or equal to9

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 (greater than or equal to20 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 (%)

 less than or equal to13 years

7.0

7.4

6.3

5.4

 145 years

19.5

20.5

20.7

17.0

 greater than or equal to16 years

18.1

16.7

19.6

22.2

 

 

 

 

 

Age at first delivery (%)

 less than or equal to21 years

16.3

16.0

18.3

20.6

 225 years

48.4

52.1

50.6

45.2

 greater than or equal to26 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

 greater than or equal to3 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.




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