Table 1 Characteristics of study participants (n = 1760), by case-control status

All

902 (100)

858 (100)

1760 (100)

Age at baseline enrollment (years)

 20–39

114 (13)

89 (10)

203 (12)

 40–44

121 (13)

125 (15)

246 (14)

 45–49

204 (23)

186 (22)

390 (22)

 50–54

196 (22)

198 (23)

394 (22)

 55–59

152 (17)

135 (16)

287 (16)

 60–80

115 (13)

125 (15)

240 (14)

Age at blood draw (years)

 40–49

38 (4)

30 (3)

68 (4)

 50–59

127 (14)

108 (13)

235 (13)

 60–69

362 (40)

369 (43)

731 (42)

 70–79

316 (35)

281 (33)

597 (34)

 ≥ 80

59 (7)

70 (8)

129 (7)

Race/Ethnicity

 White

812 (90)

763 (89)

1575 (89)

 Black

14 (2)

7 (1)

21 (1)

 Hispanic

24 (3)

32 (4)

56 (3)

 Asian/Pacific Islander

29 (3)

32 (4)

61 (3)

 Other

23 (3)

24 (3)

47 (3)

Region of Residence (CCR region)

 1:Santa Clara Region

82 (9)

83 (10)

165 (9)

 2:Central Region

99 (11)

95 (11)

194 (11)

 3:Sacramento Region

110 (12)

134 (16)

244 (14)

 4:Tri-County Region

65 (7)

62 (7)

127 (7)

 5: Inland Empire Region

42 (5)

25 (3)

67 (4)

 6:North Region

68 (8)

44 (5)

112 (6)

 7:Imperial and San Diego Region

60 (7)

48 (6)

108 (6)

 8:Bay Area Region

118 (13)

99 (12)

217 (12)

 9:Los Angeles County

173 (19)

148 (17)

321 (18)

 10:Orange County

85 (9)

120 (14)

205 (12)

Smoking pack-years

 Never smoker

580 (64)

573 (67)

1153 (66)

 ≤ 10

156 (17)

153 (18)

309 (18)

 11–20

47 (5)

60 (7)

107 (6)

 21–30

45 (5)

23 (3)

68 (4)

 ≥ 31

42 (5)

27 (3)

69 (4)

 Unknown

32 (4)

22 (3)

54 (3)

BMI at baseline (kg/m²)

 16.0–24.9

496 (55)

519 (60)

1015 (58)

 25.0–29.9

236 (26)

203 (24)

439 (25)

 30.0–53.3

153 (17)

110 (13)

263 (15)

 Unknown

17 (2)

26 (3)

43 (2)

Weight change (Q5-baseline questionnaire)

 Lost weight

161 (18)

133 (16)

294 (17)

 No change (+/−5lbs)

201 (22)

235 (27)

436 (25)

 Gained weight

346 (38)

317 (37)

663 (38)

 Unknown

194 (22)

173 (20)

367 (21)

Alcohol consumption (g/day)

 None

278 (31)

250 (29)

528 (30)

 < 20

514 (57)

507 (59)

1021 (58)

 ≥ 20

74 (8)

66 (8)

140 (8)

 Unknown

36 (4)

35 (4)

71 (4)

Physical activity (hours/week)

 < 0.50

74 (8)

51 (6)

125 (7)

 0.50–3.99

460 (51)

438 (51)

898 (51)

 ≥ 4.00

367 (41)

366 (43)

733 (42)

 Unknown

1 (0)

3 (0)

4 (0)

Family history of breast cancer

 No

728 (81)

737 (86)

1465 (83)

 Yes

136 (15)

96 (11)

232 (13)

 Unknown

38 (4)

25 (3)

63 (4)

Age at menarche (years)

 ≤ 11

227 (25)

189 (22)

416 (24)

 12–13

500 (55)

484 (56)

984 (56)

 ≥ 14

166 (18)

174 (20)

340 (19)

 Unknown/Never

9 (1)

11 (1)

20 (1)

Age at first full-term pregnancy (years)

 No full-term pregnancy

233 (26)

186 (22)

419 (24)

 ≤ 24

209 (23)

250 (29)

459 (26)

 25–29

257 (28)

257 (30)

514 (29)

 ≥ 30

193 (21)

151 (18)

344 (20)

 Unknown

10 (1)

14 (2)

24 (1)

Breast feeding history (months)

 Never pregnant

173 (19)

132 (15)

305 (17)

 Pregnancy, but no live birth

58 (6)

53 (6)

111 (6)

 0

117 (13)

125 (15)

242 (14)

 > 0 and < 6

152 (17)

130 (15)

282 (16)

 6–11

121 (13)

132 (15)

253 (14)

 ≥ 12

269 (30)

270 (31)

539 (31)

 Unknown

12 (1)

16 (2)

28 (2)

Menopausal status at time of blood draw

 Pre/Peri-menopausal

43 (5)

59 (7)

102 (6)

 Postmenopausal

859 (95)

798 (93)

1657 (94)

 Unknown

0 (0)

1 (0)

1 (0)

HT use at blood draw^c

 Never used and postmenopausal

288 (32)

237 (28)

525 (30)

 Ever used and postmenopausal

571 (63)

561 (65)

1132 (64)

 Pre/Peri-menopausal

43 (5)

59 (7)

102 (6)

 Unknown

0 (0)

1 (0)

1 (0)

HT use at baseline

 Never used

64 (7)

68 (8)

132 (8)

 Past HT use

29 (3)

37 (4)

66 (4)

 Current estrogen use

130 (14)

143 (17)

273 (16)

 Current estrogen and progesterone use

240 (27)

199 (23)

439 (25)

 Progesterone use only

6 (1)

10 (1)

16 (1)

 Pre-menopausal

399 (44)

367 (43)

766 (44)

 Unknown

34 (4)

34 (4)

68 (4)

Age at menopause (years)

 Pre/peri-menopausal

43 (5)

59 (7)

102 (6)

 20–43

143 (16)

151 (17)

294 (17)

 44–49

187 (21)

139 (16)

326 (19)

 50–51

191 (21)

161 (19)

352 (20)

 52–53

112 (12)

102 (12)

214 (12)

 54–55

111 (12)

119 (14)

230 (13)

 56–65

89 (10)

92 (11)

181 (10)

 Unknown

26 (3)

35 (4)

61 (3)

Years since onset of menopause

 Pre/peri/unknown menopausal status

43 (5)

60 (7)

103 (6)

 0–9

190 (21)

137 (16)

327 (19)

 10–19

29 (32)

305 (36)

596 (34)

 20–29

244 (27)

196 (23)

440 (25)

 30–69

116 (13)

136 (16)

252 (14)

 Unknown

18 (2)

24 (3)

42 (2)

Dietary fat

 Low tertile

270 (30)

274 (32)

544 (31)

 Middle tertile

284 (31)

261 (30)

545 (31)

 High tertile

278 (31)

269 (31)

547 (31)

 Unknown

70 (8)

54 (6)

124 (7)

Pork consumption

 None

352 (39)

374 (44)

726 (41)

 Low (< median)

193 (21)

209 (24)

402 (23)

 High (> median)

287 (32)

221 (26)

508 (29)

 Unknown

70 (8)

54 (6)

124 (7)

Total red meat consumption

 Low tertile

252 (28)

291 (34)

543 (31)

 Middle tertile

279 (31)

262 (31)

541 (31)

 High tertile

301 (33)

25 (29)

552 (31)

 Unknown

70 (8)

54 (6)

124 (7)

Neighborhood socioeconomic status

 Lowest quintile

21 (2)

25 (3)

46 (3)

 2nd quintile

69 (8)

63 (7)

132 (8)

 3rd quintile

148 (16)

137 (16)

285 (16)

 4th quintile

260 (29)

225 (26)

485 (28)

 Highest quintile

331 (37)

334 (39)

665 (38)

 Unknown

73 (8)

74 (9)

147 (8)

Neighborhood urbanization

 Rural/Town

106 (12)

90 (10)

196 (11)

 City

245 (27)

230 (27)

475 (27)

 Suburban

440 (49)

426 (50)

866 (49)

 Metro

38 (4)

38 (4)

76 (4)

Date of blood draw

 2011 Oct-Dec

19 (2)

147 (17)

166 (9)

 2012 Jan-Jun

257 (28)

151 (18)

408 (23)

 2012 Jul-Dec

155 (17)

69 (8)

224 (13)

 2013 Jan-Jun

121 (13)

142 (17)

263 (15)

 2013 Jul-Dec

91 (10)

81 (9)

172 (10)

 2014 Jan-Jun

65 (7)

67 (8)

132 (8)

 2014 Jul-Dec

100 (11)

108 (13)

208 (12)

 2015 Jan-Jun

85 (9)

82 (10)

167 (9)

 2015 Jul-Aug

9 (1)

11 (1)

20 (1)

Season of blood draw

 Winter

212 (24)

300 (35)

512 (29)

 Spring

275 (30)

173 (20)

448 (25)

 Summer

242 (27)

125 (15)

367 (21)

 Fall

173 (19)

260 (30)

433 (25)