Associations between bra-wearing characteristics and breast cancer risk
| Controls (n = 469) | Ductal cases (n = 454) | Lobular cases (n = 590) | |||
|---|---|---|---|---|---|
| Bra-wearing characteristic | n (%) | n (%) | OR (95% CI) | n (%) | OR (95% CI) |
| Lifetime average hours/day wore a bra, quartiles | |||||
| ≤10.0 | 112 (25.1) | 117 (27.1) | Ref | 152 (27.3) | Ref |
| 10.1–11.5 | 113 (25.3) | 99 (22.9) | 0.9 (0.6–1.3) | 115 (20.6) | 0.7 (0.5–1.0) |
| 11.6–13.9 | 107 (24.0) | 117 (27.1) | 1.1 (0.7–1.6) | 151 (27.1) | 0.9 (0.7–1.4) |
| ≥14 | 114 (25.6) | 99 (22.9) | 0.9 (0.6–1.3) | 139 (25.0) | 0.8 (0.6–1.2) |
| P for trend | 0.801 | 0.609 | |||
| Current average hours/day wore a bra, quartiles | |||||
| ≤10.0 | 131 (29.5) | 116 (26.9) | Ref | 165 (29.6) | Ref |
| 10.1–12.0 | 123 (27.5) | 113 (26.2) | 1.1 (0.8–1.6) | 136 (24.4) | 0.8 (0.6–1.2) |
| 12.1–15.9 | 79 (17.7) | 99 (22.9) | 1.6 (1.0–2.3) | 118 (21.2) | 1.1 (0.7–1.6) |
| ≥16 | 113 (25.3) | 104 (24.1) | 1.2 (0.8–1.8) | 138 (24.8) | 0.9 (0.6–1.3) |
| P for trend | 0.207 | 0.855 | |||
| Ever regularly wore a bra with an underwire | |||||
| No | 251 (56.4) | 233 (54.1) | Ref | 331 (59.6) | Ref |
| Yes | 194 (43.6) | 198 (45.9) | 1.2 (0.9–1.6) | 224 (40.4) | 0.8 (0.6–1.1) |
| Currently wore a bra with an underwire | |||||
| No | 283 (63.6) | 273 (63.3) | Ref | 365 (65.8) | Ref |
| Yes | 162 (36.4) | 158 (36.7) | 1.0 (0.8–1.4) | 190 (34.2) | 0.9 (0.7–1.1) |
| Current average hours/day wore a bra without underwire, quartiles | |||||
| ≤10.0 | 96 (33.9) | 87 (31.9) | Ref | 128 (35.1) | Ref |
| 10.1–12.0 | 87 (30.7) | 80 (29.3) | 1.1 (0.7–1.7) | 97 (26.6) | 0.8 (0.5–1.2) |
| 12.1–15.9 | 41 (14.5) | 51 (18.7) | 1.6 (0.9–2.7) | 70 (19.2) | 1.1 (0.7–1.9) |
| ≥16 | 59 (20.8) | 55 (20.1) | 1.2 (0.7–2.1) | 70 (19.2) | 0.8 (0.5–1.3) |
| P for trend | 0.281 | 0.713 | |||
| Current average hours/day wore a bra with an underwire, quartiles | |||||
| <9.5 | 40 (24.7) | 40 (25.3) | Ref | 48 (25.3) | Ref |
| 9.5–12.0 | 50 (30.9) | 37 (23.4) | 0.8 (0.4–1.5) | 48 (25.3) | 0.9 (0.5–1.6) |
| 12.1–15.0 | 33 (20.4) | 41 (25.9) | 1.3 (0.7–2.4) | 40 (21.1) | 1.0 (0.5–1.8) |
| ≥15.1 | 39 (24.1) | 40 (25.3) | 1.2 (0.6–2.2) | 54 (28.4) | 1.2 (0.6–2.2) |
| P for trend | 0.389 | 0.541 | |||
| Age first began wearing a bra, y | |||||
| ≤12 | 162 (34.5) | 145 (31.9) | Ref | 185 (31.4) | Ref |
| 13–14 | 217 (46.3) | 213 (46.9) | 1.1 (0.8–1.4) | 303 (51.4) | 1.2 (0.9–1.6) |
| ≥15 | 90 (19.2) | 96 (21.1) | 1.2 (0.8–1.7) | 102 (17.3) | 1.0 (0.7–1.4) |
| P for trend | 0.426 | 0.903 | |||
| Bra cup size 1 year before the reference date | |||||
| A | 17 (3.7) | 34 (7.6) | 1.9 (1.0–3.6) | 43 (7.4) | 1.8 (1.0–3.3) |
| B | 152 (32.7) | 144 (32.1) | Ref | 203 (34.9) | Ref |
| C | 166 (35.7) | 157 (35.0) | 1.0 (0.7–1.3) | 176 (30.3) | 0.8 (0.6–1.1) |
| D or above | 130 (28.0) | 113 (25.2) | 0.9 (0.7–1.3) | 159 (27.4) | 0.9 (0.7–1.3) |
| P for trend | 0.138 | 0.095 | |||
NOTE: All analysis adjusted for age at the reference date, reference year, and county.
The numbers in the column may not add up to the total case/control numbers due to missingness in some of the bra wearing variables.