Background
Methods
Study population
Cases | Controls | p-value | |
---|---|---|---|
Age at diagnosis/recruitment (years)
| |||
mean ± SD | 56.6 ± 10.1 | 52.8 ± 8.9 | <0.001 |
Place of residence (%)
| |||
Montevideo | 86.5 | 87.2 | 0.85 |
Outside Montevideo | 13.5 | 12.8 | |
Location (%)
| |||
Urbana | 85.5 | 90.6 | 0.17 |
Rural | 14.5 | 9.4 | |
Hospital (%)
| |||
Public | 87.2 | 84.8 | 0.54 |
Private | 12.8 | 15.2 | |
Age at menarche (years)
f
| |||
mean ± SD | 12.3 ± 1.5 | 12.2 ± 1.4 | 0.56 |
Oral contraceptives (%)
| |||
Yes | 66.2 | 73.8 | 0.15 |
No | 33.8 | 26.2 | |
Children (%)
t
| |||
Yes | 90.5 | 91.5 | 0.78 |
No | 9.5 | 8.5 | |
Age at first child (years)
j
| |||
mean ± SD | 25.6 ± 6.0 | 23.4 ± 6.0 | 0.01 |
Number of children (%)
i
| |||
mean ± SD | 2.46 ± 1.52 | 2.52 ± 1.73 | 0.75 |
Breastfeeding (%)
k
| |||
Yes | 80.2 | 85.5 | 0.24 |
No | 19.8 | 14.5 | |
Menopause
g,r
(%)
| |||
Yes | 65.2 | 52.1 | 0.03 |
No | 34.9 | 47.9 | |
Age at menopause (years)
h,s
| |||
mean ± SD | 49.2 ± 5.0 | 47.6 ± 4.3 | 0.07 |
Breast cancer in the family (%)
| |||
Yes | 18.2 | 9.8 | 0.03 |
No | 81.8 | 90.2 | |
Smoking (%)
l
| |||
Yes | 47.3 | 53.4 | 0.28 |
No | 52.7 | 46.6 | |
Passive smoker before 20 years old (%)
m
| |||
Yes | 55.4 | 54.0 | 0.81 |
No | 44.6 | 46.0 | |
Red meat intake
c
(%)
n,u
| |||
Yes | 95.1 | 100.0 | 0.01v |
No | 4.9 | 0.0 | |
Education (%)
| |||
Primary school | 37.8 | 32.3 | 0.001 |
Secondary school | 53.3 | 43.3 | |
University | 8.9 | 24.4 | |
Occupation (%)
o
| |||
Unemployed/never worked | 9.6 | 0.6 | <0.001v |
Self-employed | 84.3 | 70.0 | |
Public/private employee | 3.4 | 10.0 | |
Teacher | 2.7 | 4.4 | |
Retired | 0.0 | 4.4 | |
Professional | 0.0 | 10.6 | |
Income (U$S per month, %)
p
| |||
<175 | 6.1 | 7.0 | <0.001 |
175-750 | 87.0 | 66.7 | |
>750 | 6.9 | 26.3 | |
Source of income (%)
q
| |||
Social security/family | 12.2 | 3.7 | <0.001v |
Pension | 20.9 | 4.4 | |
Salary | 64.2 | 88.8 | |
Rent | 2.7 | 1.2 | |
Other | 0.0 | 1.9 | |
Socioeconomic status (%)
| |||
Low | 38.5 | 32.3 | 0.25 |
Medium | 61.5 | 67.7 | |
Weight (kg)
b
| |||
mean ± SD | 71.2 ± 14.9 | 68.5 ± 13.5 | 0.11 |
Height (m)
c
| |||
mean ± SD | 1.60 ± 0.07 | 1.59 ± 0.07 | 0.31 |
BMI (kg/m
2
)
d
| |||
mean ± SD | 27.7 ± 5.3 | 27.0 ± 5.1 | 0.22 |
Waist-hip ratio
e
| |||
mean ± SD | 0.87 ± 0.07 | 0.86 ± 0.08 | 0.17 |
Ancestry (%) mean ± SD
| |||
African | 9.8 ± 7.6 | 9.1 ± 7.5 | 0.33 |
Native American | 13.2 ± 10.2 | 14.7 ± 11.2 | 0.26 |
European | 77.1 ± 13.1 | 76.2 ± 14.2 | 0.73 |
DNA extraction
Genetic analyses
Nuclear ancestry informative markers
Mitochondrial DNA ancestry informative markers
Statistical analyses
Results
Characteristics of the study population
Ancestry and breast cancer risk
Nuclear DNA ancestry
% African (mean ± SD) | % Native American (mean ± SD) | % European (mean ± SD) | |
---|---|---|---|
Controls (N = 164)
| |||
Place of residence (N)
| |||
Montevideo (143) | 9.3 ± 7.8 | 15.3 ± 11.6 | 75.4 ± 14.7 |
Rest of the country (21) | 8.1 ± 5.2 | 10.5 ± 7.2 | 81.4 ± 7.8 |
p-value | 0.81 | 0.13 | 0.16 |
Hospital (N)
| |||
Public (139) | 9.5 ± 7.8 | 15.5 ± 11.7 | 75.1 ± 14.8 |
Private (25) | 7.4 ± 5.4 | 10.2 ± 7.0 | 82.4 ± 6.8 |
p-value | 0.27 | 0.07 | 0.05 |
Menopause (N)
| |||
Yes (91) | 8.6 ± 7.6 | 13.9 ± 10.7 | 77.5 ± 14.6 |
No (69) | 10.2 ± 7.4 | 16.1 ± 12.0 | 73.7 ± 13.4 |
p-value | 0.05 | 0.32 | 0.04 |
Breast cancer in the family (N)
| |||
Yes (16) | 8.6 ± 5.9 | 16.0 ± 12.6 | 75.4 ± 15.0 |
No (148) | 9.2 ± 7.6 | 14.5 ± 11.1 | 76.3 ± 14.1 |
p-value | 0.78 | 0.70 | 0.81 |
Education (N)
| |||
Primary school (53) | 10.0 ± 8.1 | 17.6 ± 12.3 | 72.5 ± 16.0 |
Secondary school (71) | 9.9 ± 7.9 | 15.4 ± 10.9 | 74.7 ± 13.1 |
University (40) | 6.7 ± 5.1 | 9.5 ± 8.5 | 83.8 ± 10.2 |
p-value | 0.08 | 0.001 | <0.001 |
Socioeconomic status (N)
| |||
Low (53) | 9.9 ± 8.1 | 16.7 ± 11.7 | 73.4 ± 15.6 |
Medium (111) | 8.8 ± 7.2 | 13.7 ± 10.9 | 77.5 ± 13.3 |
p-value | 0.41 | 0.07 | 0.13 |
Age at recruitment (mean change in years per 25% ancestry increase, 95% CI) (N = 164) | −0.56 (−1.75, 0.63) | 0.08 (−1.17, 1.33) | 0.52 (−0.68, 1.73) |
p-value | 0.36 | 0.90 | 0.39 |
Age at first child (mean change in years per 25% ancestry increase, 95% CI) (N = 139) | −0.44 (−1.26, 0.39) | −0.91 (−1.78, −0.03) | 0.94 (0.11, 1.78) |
p-value | 0.30 | 0.04 | 0.03 |
Age at menopause (mean change in years per 25% ancestry increase, 95% CI) (N = 49)a | −0.94 (−1.90, 0.02) | −1.60 (−2.66, −0.54) | 1.43 (0.46, 2.40) |
p-value | 0.05 | 0.004 | 0.01 |
Nuclear ancestry | ORa | 95% CI | p-value |
---|---|---|---|
European | 1.05 | (0.85,1.30) | 0.63 |
African | 1.09 | (0.89,1.33) | 0.42 |
Native American | 0.84 | (0.68,1.04) | 0.10 |
N | 312 | ||
Mitochondrial ancestry
|
OR
b
|
95% CI
|
p-value
|
European | Reference | 0.25c | |
African | 0.54 | (0.22,1.33) | 0.18 |
Native American | 0.71 | (0.42,1.20) | 0.20 |
N | 312 | ||
No H haplogroup | Reference | ||
H haplogroup | 1.99 | (1.13,3.51) | 0.02 |
N | 312 | ||
No H haplogroup | Reference | ||
H haplogroup | 1.84 | (0.97,3.51) | 0.06 |
Nd | 171 |
Mitochondrial DNA ancestry
Haplogroup | Cases | Controls | p-value |
---|---|---|---|
African | 9 | 16 | |
L | 9 | 16 | |
Native American | 55 | 65 | 0.40a |
A | 11 | 19 | |
B | 21 | 16 | |
C | 16 | 21 | |
D | 7 | 9 | |
European | 99 | 83 | 0.26a |
H | 48 | 27 | |
HV | 1 | 3 | |
I | 0 | 1 | |
J | 9 | 5 | |
K | 4 | 8 | |
N | 1 | 1 | |
R | 0 | 2 | |
T | 9 | 11 | |
U1-5 | 8 | 8 | |
U6 | 12 | 9 | |
V | 2 | 0 | |
W | 3 | 6 | |
X | 2 | 2 | |
Total | 163d | 164 | 0.20b/0.12c |