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Table 3 Case-control ORs of breast cancer risk factors by age among premenopausal women in Carolina Breast Cancer Study phases I and II (n = 1904)

From: Breast cancer biologic and etiologic heterogeneity by young age and menopausal status in the Carolina Breast Cancer Study: a case-control study

 

Age <40 years

Age ≥40 years

Test for heterogeneity

Risk factor

Control subjects, n (%)

Cases, n (%)

OR (95 % CI)a

Control subjects, n (%)

Cases, n (%)

OR (95 % CI)a

χ2 test, df (p value)b

BMI, kg/m2

 < 25.0

93 (41.9)

154 (49.2)

1.0

255 (40.0)

316 (44.3)

1.0

0.13, 2 (0.9)

 25–29.9

58 (26.1)

71 (22.7)

0.72 (0.45–1.13)

184 (28.9)

181 (25.4)

0.87 (0.65–1.14)

 

 ≥ 30.0

71 (32.0)

88 (28.1)

0.73 (0.47–1.13)

198 (31.1)

217 (30.4)

0.98 (0.74–1.29)

 

 Missing

   

12

6

  

WHR

 < 0.77

89 (41.4)

135 (44.3)

1.0

235 (36.8)

231 (32.4)

1.0

2.47, 2 (0.3)

 0.77–0.83

68 (31.6)

98 (32.1)

0.94 (0.61–1.43)

209 (32.7)

245 (34.4)

1.42 (1.08–1.86)

 

 ≥ 0.84

58 (27.0)

72 (23.6)

0.86 (0.54–1.36)

195 (30.5)

237 (33.2)

1.58 (1.18–2.11)

 

 Missing

7

8

 

10

7

  

Parity

 Nulliparous

49 (22.1)

70 (22.4)

1.0

76 (11.7)

106 (14.7)

1.0

3.55, 2 (0.2)

 1–2 births

133 (59.9)

180 (57.5)

1.05 (0.67–1.63)

383 (59.0)

420 (58.3)

0.82 (0.58–1.14)

 

 ≥ 3 births

40 (18.0)

63 (20.1)

1.29 (0.74–2.27)

190 (29.3)

194 (26.9)

0.81 (0.55–1.18)

 

History of breastfeedingc

 Never

77 (44.5)

145 (60.2)

1.0

343 (60.2)

370 (60.6)

1.0

9.01, 1 (0.003)

 Ever

96 (55.5)

96 (39.8)

0.48 (0.31–0.75)

227 (39.8)

241 (39.4)

0.90 (0.70–1.16)

 

Lifetime breastfeeding durationc

 Never

86 (49.7)

148 (61.4)

1.0

346 (60.7)

378 (61.9)

1.0

6.36, 2 (0.04)

 > 0–3 months

25 (14.5)

33 (13.7)

0.79 (0.43–1.45)

69 (12.1)

65 (10.6)

0.86 (0.58–1.25)

 

 ≥ 4 months

62 (35.8)

60 (24.9)

0.50 (0.30–0.81)

155 (27.2)

168 (27.5)

0.87 (0.65–1.15)

 

Time since last term pregnancyc

 < 10 years

119 (68.8)

169 (70.1)

1.0

76 (13.3)

108 (17.7)

1.0

4.44, 2 (0.1)

 10–19 years

50 (28.9)

66 (27.4)

1.02 (0.64–1.63)

302 (53.0)

283 (46.3)

0.71 (0.50–1.01)

 

 ≥ 20 years

4 (2.3)

6 (2.5)

1.14 (0.30–4.27)

192 (33.7)

220 (36.0)

0.96 (0.64–1.43)

 

Age at first live birthc

 < 26 years

103 (59.5)

146 (60.6)

1.0

386 (67.7)

414 (67.8)

1.0

0.00, 1 (1.0)

 ≥ 26 years

70 (40.5)

95 (39.4)

1.03 (0.68–1.58)

184 (32.3)

197 (32.2)

0.93 (0.71–1.20)

 

Age at last live birthc

 < 30 years

102 (59.0)

148 (61.4)

1.0

344 (60.4)

362 (59.2)

1.0

0.01, 1 (0.9)

 ≥ 30 years

71 (41.0)

93 (38.6)

1.01 (0.67–1.54)

226 (35.6)

249 (40.8)

0.99 (0.78–1.26)

 

Age at menarche

 < 13 years

111 (50.2)

170 (54.3)

1.0

323 (49.8)

393 (54.6)

1.0

0.01, 1 (0.9)

 ≥ 13 years

110 (49.8)

143 (45.7)

0.85 (0.59–1.20)

326 (50.2)

327 (45.4)

0.83 (0.66–1.03)

 

 Missing

1

      

Oral contraceptive use

 Never

33 (14.9)

36 (11.5)

1.0

112 (17.3)

125 (17.4)

1.0

0.67, 1 (0.4)

 Ever

189 (85.1)

276 (88.5)

1.32 (0.78–2.22)

534 (82.7)

593 (82.6)

0.93 (0.70–1.25)

 

 Missing

 

1

 

3

2

  
  1. BMI body mass index, WHR waist-to-hip ratio
  2. aAdjusted for matching factors race and age
  3. bLikelihood ratio tests were performed to assess age-related heterogeneity in risk factor associations by comparing the estimated log-likelihood of adjusted models with that of the adjusted model including a multiplicative interaction term for age and the corresponding risk factor (e.g., BMI × age). Statistically significant heterogeneity by age was defined with α = 0.1
  4. cAmong parous women
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Breast Cancer Research

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