Table 1 Incidence of breast cancer by characteristics of the participants of the SBSP
Characteristics | No. of subjects | No. of cases | Person years | Incidence (/100,000 PYs) | HR (95% CI) |
|---|---|---|---|---|---|
All subjects | 14464 | 66 | 34001 | 194 | — |
Age (yrs.) | |||||
    < 40 | 1020 | 0 | 2122 | 0 | — |
    40- | 2833 | 9 | 6848 | 131 | 0.60 (0.28, 1.27) |
    50- | 5349 | 29 | 13200 | 220 | 1.00 (ref.) |
    60- | 4213 | 23 | 9712 | 237 | 1.07 (0.62, 1.85) |
    70- | 1049 | 5 | 2118 | 236 | 1.05 (0.40, 2.72) |
Education | |||||
    Primary school or No formal education | 3324 | 17 | 8940 | 190 | 1.23 (0.62, 2.44) |
    Junior middle school | 5646 | 18 | 13361 | 135 | 1.00 (ref.) |
    Senior high school or technical school | 3739 | 21 | 8099 | 259 | 1.86 (0.99, 3.49) |
    Junior college | 1018 | 6 | 2148 | 279 | 2.44 (0.96, 6.19) |
    Regular college or above | 737 | 4 | 1454 | 275 | 2.91 (0.97, 8.72) |
Family history of breast cancer | |||||
    Yes | 366 | 5 | 858 | 583 | 3.03 (1.22, 7.54) |
    No | 14098 | 61 | 33143 | 184 | 1.00 (ref.) |
Age at menarche (yrs.) | |||||
    ≤ 13 | 2078 | 15 | 4582 | 327 | 1.99 (1.10, 3.58) |
    14-17 | 10330 | 44 | 24273 | 181 | 1.00 (ref.) |
    > 17 | 2053 | 7 | 5142 | 136 | 0.66 (0.29, 1.47) |
Menopausal status | |||||
    Pre-menopause | 4455 | 12 | 10510 | 114 | 0.81 (0.32, 2.04) |
    Post-menopause | 9996 | 54 | 23462 | 230 | 1.00 (ref.) |
Age at menopause (yrs.) | |||||
    < 45 | 721 | 4 | 1704 | 235 | 1.12 (0.41, 3.11) |
    45-54 | 8323 | 44 | 19523 | 225 | 1.00 (ref.) |
    ≥ 55 | 952 | 6 | 2234 | 269 | 1.20 (0.51, 2.81) |
Age at first live birth (yrs.) | |||||
    Nulliparity | 299 | 0 | 643 | 0 | — |
    < 24 | 3290 | 13 | 7940 | 164 | 0.99 (0.51, 1.92) |
    24-29 | 9121 | 39 | 21691 | 180 | 1.00 (ref.) |
    ≥ 30 | 1750 | 14 | 3718 | 377 | 2.01 (1.09, 3.71) |