Background
Methods
Study Participants
Measures of SES
Mammographic Density Measurements
Statistical Analysis
Participant baseline characteristics
| n | Mean | SD | |
---|---|---|---|---|
Age at mammography (yrs) | 487 | 48.6 | 1.6 | |
Weight (kg) | 487 | 67.6 | 12.9 | |
Age at menarche (yrs) | 194 | 13.1 | 1.5 | |
n
|
%
|
Median PD (25
th
, 75
th
)
1
| ||
Smoking | 487 | |||
Never | 273 | 56 | 26.7 (13.7, 43.5) | |
Ex smoker | 152 | 31 | 29.5 (14.1, 46.7) | |
Current | 62 | 13 | 27.2 (10.5, 42.7) | |
Height (m) | 487 | |||
<1.60 | 158 | 32 | 24.9 (13.3, 43.8) | |
1.60-1.64 | 137 | 28 | 26.9 (12.3, 43.5) | |
1.65-1.69 | 110 | 23 | 28.6 (15.4, 43.4) | |
≥ 1.7 | 82 | 17 | 31.1 (18.2, 43.0) | |
BMI (kg/m2) | 487 | |||
<22 | 115 | 24 | 46.0 (32.1, 61.6) | |
22-24.9 | 145 | 30 | 31.5 (19.5, 43.1) | |
25-27.9 | 115 | 24 | 22.1 (11.6, 37.4) | |
≥ 28 | 112 | 23 | 9.5 (4.0, 21.6) | |
Number of full-term pregnancies | 487 | |||
0 | 63 | 13 | 32.9 (10.4, 53.6) | |
1-2 | 297 | 61 | 28.7 (14.2, 45.6) | |
3+ | 127 | 26 | 23.5 (13.8, 39.0) | |
Age at first full-term pregnancy2
| 424 | |||
<24 years | 140 | 33 | 22.7 (12.0, 37.8) | |
24-28.9 years | 160 | 38 | 26.3 (14.6, 42.4) | |
≥ 29 years | 124 | 29 | 31.6 (16.1, 49.7) | |
Family history of breast cancer | 487 | |||
Yes | 53 | 11 | 28.6 (15.8, 46.5) | |
No | 434 | 89 | 27.5 (13.7, 43.4) | |
Lifetime breast feeding2,3
| 326 | |||
Never | 55 | 17 | 21.6 (9.4, 37.9) | |
1-6 months | 90 | 28 | 28.4 (13.3, 39.7) | |
7-12 months | 60 | 18 | 30.0 (15.5, 52.6) | |
≥ 13 months | 121 | 37 | 32.1 (16.4, 47.2) |
Results
Participant Characteristics
Measures of mammographic density
| n | Median | 25th percentile | 75th percentile | |
---|---|---|---|---|---|
Dense area (cm2) | 487 | 35.3 | 18.4 | 51.7 | |
Lucent area (cm2) | 487 | 92.4 | 60.5 | 134.7 | |
Percent density (%) | 487 | 27.7 | 13.7 | 43.5 | |
Measures of socioeconomic status
|
n
|
%
|
Median PD (25
th
, 75
th
)
1
| ||
Townsend score2
| 487 | ||||
Q5 (affluent) | 160 | 33 | 31.1 (16.4, 46.5) | ||
Q4 | 133 | 27 | 29.0 (15.2, 46.0) | ||
Q3 | 99 | 20 | 25.2 (9.4, 41.8) | ||
Q2 | 56 | 12 | 23.4 (11.2, 40.1) | ||
Q1 (deprived) | 39 | 8 | 21.6 (11.7, 34.6) | ||
Highest education level | 369 | ||||
Higher (University) | 139 | 38 | 33.0 (17.7, 51.6) | ||
Further (A-level/vocational) | 82 | 22 | 23.6 (11.9, 40.6) | ||
None to GCSE | 148 | 40 | 25.2 (11.6, 38.6) | ||
Urban/Rural indicator | 487 | ||||
Rural (Population <10,000) | 61 | 13 | 28.1 (15.8, 46.0) | ||
Urban (Population ≥ 10,000) | 426 | 87 | 27.6 (12.9, 43.1) |
Percent density1,2
| Dense area3
| Lucent area4
| ||
---|---|---|---|---|
BMI (kg/m2) (n = 487) | <22 | 0 | 0 | 0 |
22-24.9 | -10.6 (-14.0,-6.9) | -6.0 (-10.8,-0.8) | 36.2 (24.7,48.2) | |
25-27.9 | -17.3 (-20.1,-14.1) | -10.9 (-15.5,-5.9) | 66.4 (52.8,80.6) | |
≥ 28 | -24.6 (-26.4,-22.5) | -19.4 (-23.1,-15.3) | 131.6 (115.3,148.4) | |
P-value for linear trend | Pt < 0.001 | Pt < 0.001 | Pt < 0.001 |
SES Variable | Ratio1 (95% CI) | P-value2
| |
---|---|---|---|
Townsend score | Q53 (affluent) | 1 | |
(n = 487) | Q4 | 1.01 (0.97, 1.05) | |
Q3 | 1.04 (0.99, 1.08) | Pt = 0.001 | |
Q2 | 1.07 (1.01, 1.12) | ||
Q1 (deprived) | 1.08 (1.02, 1.15) | ||
Highest educational level | Higher | 1 | |
(n = 369) | Further | 1.03 (0.98, 1.08) | Pt = 0.15 |
None/GCSE | 1.03 (0.99, 1.07) | ||
Urban/Rural indicator | Rural (≥10,000) | 1 | Pt = 0.26 |
(n = 487) | Urban (<10,000) | 1.03 (0.98, 1.08) |
Main Findings
SES Variable | Percent density1
| P-value2
| Dense area3
| P-value2
| Lucent area4
| P-value2
|
---|---|---|---|---|---|---|
Highest education level
| ||||||
Minimally-adjusted5
| ||||||
Higher | 0 | 0 | 0 | |||
Further | -6.3 (-11.3,-0.8) | 0.01 | -6.2 (-11.8,0.0) | 0.09 | 15.8 (0.0,32.8) | 0.005 |
None/GCSE | -6.3 (-10.5,-1.6) | -4.7 (-9.6,0.7) | 19.3 (5.6,33.8) | |||
+ BMI-adjusted6
| ||||||
Higher | 0 | 0 | 0 | |||
Further | -4.3 (-8.8,0.6) | 0.06 | -4.8 (-10.3,1.3) | 0.25 | 8.2 (-3.7,20.8) | 0.04 |
None/GCSE | -4.0 (-7.9,0.1) | -3.1 (-8.0,2.2) | 10.7 (0.6,21.5) | |||
Fully-adjusted7
| ||||||
Higher | 0 | 0 | 0 | |||
Further | -4.1 (-8.8,1.1) | 0.09 | -4.2 (-10.1,2.3) | 0.29 | 8.1 (-4.3,21.4) | 0.07 |
None/GCSE | -4.0 (-8.3,0.7) | -3.2 (-8.6,2.8) | 10.7 (-0.8,22.9) | |||
Townsend score
8
| ||||||
Minimally-adjusted5
| ||||||
Q5 (affluent) | 0 | 0 | 0 | |||
Q4 | -1.4 (-6.0,3.8) | -0.9 (-6.2,4.7) | 4.3 (-8.0,17.5) | |||
Q3 | -5.1 (-9.8,0.2) | 0.01 | -4.4 (-9.8,1.4) | 0.18 | 12.2 (-1.7,27.1) | <0.001 |
Q2 | -6.0 (-11.5,0.3) | -3.0 (-9.6,4.3) | 23.1 (5.4,42.2) | |||
Q1 (deprived) | -6.6 (-12.9,0.7) | -3.3 (-10.8,5.2) | 28.0 (7.3,50.7) | |||
+ BMI-adjusted6
| ||||||
Q5 (affluent) | 0 | 0 | 0 | |||
Q4 | -0.2 (-4.2,4.2) | -0.1 (-5.1,5.3) | 0.9 (-8.4,10.6) | |||
Q3 | -2.0 (-6.2,2.6) | 0.92 | -2.2 (-7.4,3.5) | 0.81 | 2.1 (-8.0,12.7) | 0.47 |
Q2 | 0.1 (-5.2,6.0) | 1.3 (-5.4,8.7) | 3.2 (-9.1,16.5) | |||
Q1 (deprived) | 0.6 (-5.6,7.5) | 1.8 (-6.0,10.5) | 4.4 (-10.0,19.9) | |||
Fully-adjusted7
| ||||||
Q5 (affluent) | 0 | 0 | 0 | |||
Q4 | 0.1 (-4.0, 4.6) | 0.2 (-4.9,5.6) | 0.2 (-9.1,10.1) | |||
Q3 | -1.2 (-5.7, 3.5) | 0.76 | -1.2 (-6.6,4.8) | 0.53 | 1.3 (-9.1,12.3) | 0.61 |
Q2 | 0.8 (-4.7, 6.8) | 2.1 (-4.8,9.7) | 2.4 (-10.2,15.9) | |||
Q1 (deprived) | 1.8 (-4.7, 9.1) | 3.1 (-5.1,12.3) | 3.2 (-11.6,19.3) | |||
Urban/Rural indicator
| ||||||
Minimally-adjusted5
| ||||||
Rural (<10,000 people) | 0 | 0.34 | 0 | 0.66 | 0 | 0.17 |
Urban (≥ 10,000 people) | -2.8 (-8.0, 3.0) | -1.4 (-7.3,5.1) | 10.4 (-4.3,26.2) | |||
+ BMI-adjusted6
| ||||||
Rural (<10,000 people) | 0 | 0.98 | 0 | 0.92 | 0 | 0.71 |
Urban (≥ 10,000 people) | -0.1 (-4.7, 4.9) | 0.3 (-5.5,6.6) | 2.1 (-8.5,13.4) | |||
Fully-adjusted7
| ||||||
Rural (<10,000 people) | 0 | 0.81 | 0 | 0.69 | 0 | 0.81 |
Urban (≥ 10,000 people) | 0.6 (-4.2,5.8) | 1.3 (-4.7,7.8) | 1.4 (-9.5,13.0) |
SES Variable | Percent density1
| P-value2
| Dense area3
| P-value2
| Lucent area4
| P-value2
|
---|---|---|---|---|---|---|
Minimally-adjusted
5
| ||||||
Level of education | ||||||
Higher | 0 | 0 | 0 | |||
Further | -6.3 (-11.3,-0.7) | 0.02 | -6.3 (-11.9,-0.0) | 0.11 | 15.0 (-0.7,32.0) | 0.01 |
None/GCSE | -5.9 (-10.2,-1.1) | -4.4 (-9.4,1.0) | 17.2 (3.5,31.8) | |||
Townsend Score6
| ||||||
Q5 (affluent) | 0 | 0 | 0 | |||
Q4 | -2.0 (-7.2,3.8) | -1.7 (-7.5,4.7) | 6.4 (-7.9,21.9) | |||
Q3 | -2.4 (-8.0,3.9) | 0.38 | -1.4 (-7.8,5.6) | 0.96 | 7.7 (-8.0,24.8) | 0.04 |
Q2 | -0.7 (-7.9,7.5) | 3.3 (-5.1,12.8) | 14.7 (-5.6,37.1) | |||
Q1 (deprived) | -5.1 (-13.5,5.1) | -2.8 (-12.6,8.8) | 24.4 (-2.8,55.3) | |||
BMI-adjusted
7
| ||||||
Highest education level | ||||||
Higher | 0 | 0 | 0 | |||
Further | -4.4 (-8.9,0.6) | 0.06 | -4.9 (-10.5,1.2) | 0.25 | 7.9 (-4.0,20.6) | 0.05 |
None/GCSE | -4.0 (-7.9,0.2) | -3.2 (-8.1,2.2) | 10.4 (0.1,21.3) | |||
Townsend score6
| ||||||
Q5 (affluent) | 0 | 0 | 0 | |||
Q4 | -0.9 (-5.5,4.0) | -0.9 (-6.6,5.2) | 2.9 (-8.1,14.6) | |||
Q3 | 0.2 (-4.9,5.8) | 0.51 | 0.4 (-5.9,7.3) | 0.34 | -1.0 (-12.7,11.6) | 0.73 |
Q2 | 3.2 (-3.5,10.5) | 5.8 (-2.6,15.2) | 2.9 (-12.0,19.2) | |||
Q1 (deprived) | 0.5 (-7.7,10.0) | 1.1 (-9.2,12.9) | 5.0 (-14.7,26.9) |