Table 5 Oral contraceptive use in relation to breast cancer risk, stratified by menopausal status and parity a
Controls ( n ) | Cases ( n ) | OR | (95% CI) | Controls ( n ) | Cases ( n ) | OR | (95% CI) | |
|---|---|---|---|---|---|---|---|---|
Premenopausal women | Postmenopausal women | |||||||
Never users | 1,371 | 363 | 1.00 | Reference | 2,903 | 854 | 1.00 | Reference |
Ever users | 2,667 | 767 | 1.24 | (1.05 to 1.45) | 2,184 | 703 | 1.16 | (1.01 to 1.33) |
OC recency | ||||||||
< 5 years ago | 937 | 273 | 1.54 | (1.25 to 1.90) | 90 | 19 | 1.02 | (0.59 to 1.76) |
5 to 9 years ago | 404 | 113 | 1.31 | (1.01 to 1.72) | 99 | 21 | 0.85 | (0.50 to 1.44) |
≥ 10 years ago | 1,324 | 380 | 1.08 | (0.90 to 1.30) | 1,989 | 654 | 1.17 | (1.02 to 1.34) |
P trend | <0.01 | 0.39 | ||||||
OC duration | ||||||||
< 5 years | 1,066 | 276 | 1.11 | (0.91 to 1.35) | 992 | 301 | 1.14 | (0.96 to 1.36) |
5 to 9 years | 818 | 217 | 1.14 | (0.92 to 1.41) | 648 | 222 | 1.24 | (1.02 to 1.50) |
≥ 10 years | 782 | 274 | 1.53 | (1.25 to 1.88) | 542 | 175 | 1.09 | (0.88 to 1.34) |
P trend | <0.01 | 0.83 | ||||||
Nulliparous women | Parous women | |||||||
Never users | 917 | 244 | 1.00 | Reference | 3,706 | 1,046 | 1.00 | Reference |
Ever users | 1,230 | 267 | 1.09 | (0.87 to 1.38) | 4,183 | 1,338 | 1.21 | (1.08 to 1.35) |
OC recency | ||||||||
< 5 years ago | 406 | 93 | 1.37 | (0.98 to 1.92) | 669 | 211 | 1.55 | (1.26 to 1.90) |
5 to 9 years ago | 160 | 22 | 0.77 | (0.46 to 1.29) | 383 | 126 | 1.39 | (1.08 to 1.77) |
≥ 10 years ago | 663 | 151 | 1.05 | (0.81 to 1.36) | 3,123 | 982 | 1.15 | (1.03 to 1.29) |
P trend | 0.16 | <0.01 | ||||||
OC duration | ||||||||
< 5 years | 438 | 89 | 1.06 | (0.79 to 1.44) | 1,875 | 538 | 1.11 | (0.97 to 1.27) |
5 to 9 years | 361 | 76 | 1.08 | (0.78 to 1.50) | 1,268 | 405 | 1.22 | (1.05 to 1.42) |
≥ 10 years | 431 | 102 | 1.13 | (0.84 to 1.52) | 1,037 | 390 | 1.37 | (1.17 to 1.60) |
P trend | 0.61 | 0.01 | ||||||