Table 2 Demographic, personal and lifestyle characteristics among 1,641 Caucasian breast cancer cases and controls, Mayo Clinic 2001 to 2005

Age (years)

20 to 39

56

7

48

6

40 to 49

192

24

166

20

50 to 59

224

28

274

32

60 to 69

195

24

207

25

70+

131

16

148

18

State of residence

Minnesota

502

63

552

66

Wisconsin

69

9

78

9

Iowa

128

16

147

17

North Dakota/South Dakota

52

6

41

5

Illinois

47

6

25

3

Body mass index (kg/m²)

Mean (standard deviation)

28

8

27

8

Family history^b

Yes

366

47

345

43

Postmenopausal status

Yes

480

64

579

72

Age at menarche (years)

<12

132

18

122

16

12

224

31

184

24

13

218

30

238

32

≥ 14

154

21

209

28

Oral contraceptive use

0 months

266

35

243

31

1 to 48 months

185

24

189

24

48+ months

310

41

345

44

Postmenopausal hormone use

0 months

430

58

366

49

1 to 60 months

131

18

160

22

60+ months

184

25

216

29

Age at first birth (years)

Nulliparous

97

13

128

16

≤ 20 years

173

22

158

20

>20 years

501

65

514

64

Smoking (pack years)

None

467

63

500

66

≤ 4 years

46

6

67

9

>4 years

231

31

192

25

Alcohol consumption

Never

92

12

94

12

Monthly

332

43

327

41

Weekly

259

34

299

37

Daily

83

11

79

10