Supplemental Table S2.Association of non-dense area with breast cancer, by the level of breast cancer risk factor a.

Breast cancer risk factor / Non-dense area b / p for trend / P for interaction
1st quartile (reference) / 2nd quartile / 3rd quartile / 4th quartile
N
Cases/
Controls / OR / N
Cases/
Controls / OR
(95% CI) / N
Cases/
Controls / OR
(95% CI) / N
Cases/
Controls / OR
(95% CI)
Alcohol consumption, g/day
0
>0-<5
≥5 / 104/149
115/132
121/154 / 1.00
1.00
1.00 / 87/158
69/142
75/134 / 0.69 (0.47-1.01)
0.52 (0.35-0.79)
0.74 (0.49-1.10) / 97/153
48/151
68/126 / 0.77 (0.52-1.14)
0.32 (0.20-0.50)
0.67 (0.43-1.03) / 104/180
59/158
56/93 / 0.60 (0.38- 0.92)
0.35 (0.21-0.56)
0.75 (0.45-1.23) / 0.05
<0.0001
0.25 / 0.66
History of benign breast disease
No
Yes / 212/326
140/120 / 1.00
1.00 / 164/339
79/113 / 0.65 (0.50- 0.85)
0.61 (0.41-0.91) / 160/325
66/121 / 0.60 (0.45- 0.80)
0.47 (0.31- 0.72) / 159/339
64/108 / 0.50 (0.36- 0.69)
0.53 (0.33- 0.84) / <0.001
0.01 / 0.14
Family history of breast cancer
No
Yes / 286/382
66/64 / 1.00
1.00 / 197/388
46/64 / 0.63 (0.50-0.80)
0.69 (0.39-1.21) / 181/379
45/67 / 0.56 (0.43-0.73)
0.55 (0.30-1.00) / 176/383
47/64 / 0.51 (0.38- 0.68)
0.50 ( 0.26-0.96) / <0.0001
0.04 / 0.64
Postmenopausal hormone use (PMH)
None
Past
Current / 49/102
57/95
236/235 / 1.00
1.00
1.00 / 53/122
45/100
137/215 / 0.82 (0.49-1.36)
0.66 (0.40-1.10)
0.58 (0.43- 0.78) / 43/126
53/117
119/189 / 0.55 (0.32-0.96)
0.64 ( 0.38-1.08)
0.55 (0.40- 0.75) / 67/131
45/112
100/191 / 0.72 (0.41-1.29)
0.50 (0.28- 0.92)
0.42 (0.30-0.61) / 0.33
0.04
<0.0001 / 0.04
Age at menarche, yrs
<12
12-13
>13 / 73/78
202/254
77/114 / 1.00
1.00
1.00 / 56/90
141/256
46/106 / 0.58 (0.36-0.96)
0.68 (0.51-0.91)
0.60 (0.37- 0.97) / 52/107
128/258
46/81 / 0.42 (0.25-0.71)
0.57 (0.41-0.78)
0.78 (0.47-1.31) / 60/120
130/249
33/78 / 0.42 (0.24- 0.74)
0.56 (0.39-0.79)
0.52 (0.29-0.95) / <0.01
<0.01
0.07 / 0.46
Nulliparityc
Nulliparous
Parous / 31/33
321/413 / 1.00
1.00 / 15/27
228/425 / 0.60 (0.24-1.52)
0.63 (0.50-0.80) / 16/21
210/425 / 0.80 (0.27-2.35)
0.54 (0.43-0.69) / 21/22
202/425 / 1.49 (0.51-4.37)
0.47 (0.36-0.62) / 0.27
<0.0001 / 0.03
Parityd
1
2
≥3 / 30/31
95/119
192/262 / 1.00
1.00
1.00 / 14/17
53/98
157/306 / 0.52 (0.18-1.50)
0.63 (0.40-0.99)
0.63 (0.48-0.84) / 15/18
53/105
140/298 / 0.54 (1.20-1.49)
0.59 (0.37-0.95)
0.53 (0.39-0.72) / 12/30
44/102
139/291 / 0.17 (0.05-0.63)
0.47 (0.27-0.80)
0.49 (0.35-0.68) / 0.01
0.01
<0.001 / 0.17
Age at 1stchild’s birth, yrse
≤25
>25 / 158/191
159/221 / 1.00
1.00 / 109/234
115/187 / 0.49 (0.35-0.69)
0.82 (0.59-1.14) / 101/219
107/202 / 0.45 (0.32-0.65)
0.66 (0.47-0.93) / 94/223
101/200 / 0.38 (0.25-0.56)
0.57 (0.38-0.84) / <0.0001
<0.01 / 0.31
Body Mass Index, kg/m2
<25
25-<30
≥30 / 252/343
89/88
11/15 / 1.00
1.00
1.00 / 110/210
98/186
35/56 / 0.71 (0.53-0.95)
0.50 (0.34-0.75)
0.83 (0.33-2.10) / 78/163
86/176
62/107 / 0.65 (0.46-0.90)
0.44 (0.29-0.67)
0.76 (0.31-1.82) / 36/114
89/144
98/189 / 0.42 (0.27-0.66)
0.54 (0.35-0.84)
0.65 (0.27-1.56) / <0.0001
0.05
0.22 / 0.07
Physical activity (mets/week)
<4.4
4.4-<12
12-<25.5
≥ 25.5 / 79/99
92/100
93/122
88/125 / 1.00
1.00
1.00
1.00 / 59/107
79/113
46/113
59/119 / 0.55 (0.34-0.90)
0.76 (0.49-1.18)
0.45 (0.28-0.71)
0.70 (0.45-1.09) / 59/121
59/89
58/115
50/121 / 0.52 (0.31-0.85)
0.65 (0.40-1.06)
0.49 (0.30-0.78)
0.54 (0.33-0.87) / 72/143
48/118
49/99
54/87 / 0.46 (0.27-0.80)
0.37 (0.22- 0.65)
0.48 (0.28-0.80)
0.78 (0.45-1.35) / 0.02
<0.001
0.02
0.34 / 0.08
Age at menopause, yrs
<50
50-<55
≥55 / 111/137
207/264
20/24 / 1.00
1.00
1.00 / 78/146
146/279
16/25 / 0.63 (0.43-0.94)
0.62 (0.46-0.82)
0.70 (0.27-1.85) / 66/131
141/282
17/30 / 0.56 (0.37-0.87)
0.54 (0.40-0.73)
0.80 (0.30-2.17) / 73/147
135/269
15/30 / 0.52 (0.33-0.82)
0.49 (0.35-0.70)
0.63 (0.22-1.82) / 0.01
<0.001
0.45 / 0.69

a Multivariate models in stratified analyses are adjusted for the following covariates (with the exception of the covariate used for stratification) : age at diagnosis (continuous, years), body mass index (continuous, kg/m2), age at menarche (<12, 12-13, or >13 years), parity and age at first birth (i.e., age at the end of the first pregnancy lasting ≥6 months, modeled as nulliparous, any number of children with age at birth<25 years, any number of children with age at birth ≥25 years), menopausal hormone therapy (never used hormones, current hormone use, past hormone use), age at menopause (50, 50–<55, ≥55 years), a family history of breast cancer (yes or no), a biopsy-confirmed history of benign breast disease (yes vs. no), alcohol consumption (0, <5, or ≥5 g/day), and smoking status (ever vs. never)

b Non-dense area quartiles are defined as follows: 1st: <80 cm2; 2nd: 80-<133 cm2; 3rd: 133-<203 cm2; 4th: ≥203 cm2

c Multivariate models in stratified analyses are adjusted for the following covariates: age at diagnosis (continuous, years), body mass index (continuous, kg/m2), age at menarche (<12, 12-13, or >13 years), age at first birth (among parous only, continuous), menopausal hormone therapy (never used hormones, current hormone use, past hormone use), age at menopause (50, 50–<55, ≥55 years), a family history of breast cancer (yes or no), a biopsy-confirmed history of benign breast disease (yes vs. no), alcohol consumption (0, <5, or ≥5 g/day), and smoking status (ever vs. never)

dAmong parous women only; multivariate models in stratified analyses are adjusted for age at diagnosis (continuous, years), body mass index (continuous, kg/m2), age at menarche (<12, 12-13, or >13 years), age at first birth (continuous), menopausal hormone therapy (never used hormones, current hormone use, past hormone use), age at menopause (50, 50–<55, ≥55 years), a family history of breast cancer (yes or no), a biopsy-confirmed history of benign breast disease (yes vs. no), alcohol consumption (0, <5, or ≥5 g/day), and smoking status (ever vs. never)

e Among parous women only; multivariate models in stratified analyses are adjusted for age at diagnosis (continuous, years), body mass index (continuous, kg/m2), age at menarche (<12, 12-13, or >13 years), parity (continuous), menopausal hormone therapy (never used hormones, current hormone use, past hormone use), age at menopause (50, 50–<55, ≥55 years), a family history of breast cancer (yes or no), a biopsy-confirmed history of benign breast disease (yes vs. no), alcohol consumption (0, <5, or ≥5 g/day), and smoking status (ever vs. never)