Table 1.
Characteristics of the nested case‐control sample
| Total (N = 258) | Case (N = 86) | Control (N = 172) | P‐value | ||||
|---|---|---|---|---|---|---|---|
| Benign breast disease (BBD) | |||||||
| Nonproliferative (N, %) | 168 | 65.1% | 56 | 65.1% | 112 | 65.1% | 1.00b |
| Proliferative without atypia (N, %) | 78 | 30.2% | 26 | 30.2% | 52 | 30.2% | |
| Proliferative with atypia (N, %) | 12 | 4.7% | 4 | 4.7% | 8 | 4.7% | |
| Age at BBD diagnosis, years | |||||||
| Mean, SD | 56.4 | 0.3 | 56.3 | 0.5 | 56.5 | 0.4 | 0.70c |
| Median (Range) | 56 | (49–68) | 55 | (50–68) | 56 | (49–67) | |
| Age groups | |||||||
| 50–54 (N, %) | 103 | 39.9% | 36 | 41.9% | 67 | 39.0% | 0.50b |
| 55–59 (N, %) | 78 | 30.2% | 29 | 33.7% | 49 | 28.5% | |
| 60–64 (N, %) | 66 | 25.6% | 19 | 22.1% | 47 | 27.3% | |
| 65–68 (N, %) | 11 | 4.3% | 2 | 2.3% | 9 | 5.2% | |
| Years since BBDa, months | |||||||
| Mean, SD | 70.0 | 2.5 | 71.4 | 4.6 | 69.2 | 3.0 | 0.69c |
| Median (Range) | 63.5 | (12–193) | 67.0 | (18–193) | 62.0 | (12–183) | |
a
Follow‐up time between year of BBD diagnosis and the end of follow‐up.
b
Chi‐squared test comparing distributions of characteristics across case‐control status.
c
Two‐sample t‐tests comparing means across case‐control status.