Table 2.

Associations between bra-wearing characteristics and breast cancer risk

Controls (n = 469)Ductal cases (n = 454)Lobular cases (n = 590)
Bra-wearing characteristicn (%)n (%)OR (95% CI)n (%)OR (95% CI)
Lifetime average hours/day wore a bra, quartiles
 ≤10.0112 (25.1)117 (27.1)Ref152 (27.3)Ref
 10.1–11.5113 (25.3)99 (22.9)0.9 (0.6–1.3)115 (20.6)0.7 (0.5–1.0)
 11.6–13.9107 (24.0)117 (27.1)1.1 (0.7–1.6)151 (27.1)0.9 (0.7–1.4)
 ≥14114 (25.6)99 (22.9)0.9 (0.6–1.3)139 (25.0)0.8 (0.6–1.2)
P for trend0.8010.609
Current average hours/day wore a bra, quartiles
 ≤10.0131 (29.5)116 (26.9)Ref165 (29.6)Ref
 10.1–12.0123 (27.5)113 (26.2)1.1 (0.8–1.6)136 (24.4)0.8 (0.6–1.2)
 12.1–15.979 (17.7)99 (22.9)1.6 (1.0–2.3)118 (21.2)1.1 (0.7–1.6)
 ≥16113 (25.3)104 (24.1)1.2 (0.8–1.8)138 (24.8)0.9 (0.6–1.3)
P for trend0.2070.855
Ever regularly wore a bra with an underwire
 No251 (56.4)233 (54.1)Ref331 (59.6)Ref
 Yes194 (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
 No283 (63.6)273 (63.3)Ref365 (65.8)Ref
 Yes162 (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
 ≤10.096 (33.9)87 (31.9)Ref128 (35.1)Ref
 10.1–12.087 (30.7)80 (29.3)1.1 (0.7–1.7)97 (26.6)0.8 (0.5–1.2)
 12.1–15.941 (14.5)51 (18.7)1.6 (0.9–2.7)70 (19.2)1.1 (0.7–1.9)
 ≥1659 (20.8)55 (20.1)1.2 (0.7–2.1)70 (19.2)0.8 (0.5–1.3)
P for trend0.2810.713
Current average hours/day wore a bra with an underwire, quartiles
 <9.540 (24.7)40 (25.3)Ref48 (25.3)Ref
 9.5–12.050 (30.9)37 (23.4)0.8 (0.4–1.5)48 (25.3)0.9 (0.5–1.6)
 12.1–15.033 (20.4)41 (25.9)1.3 (0.7–2.4)40 (21.1)1.0 (0.5–1.8)
 ≥15.139 (24.1)40 (25.3)1.2 (0.6–2.2)54 (28.4)1.2 (0.6–2.2)
P for trend0.3890.541
Age first began wearing a bra, y
 ≤12162 (34.5)145 (31.9)Ref185 (31.4)Ref
 13–14217 (46.3)213 (46.9)1.1 (0.8–1.4)303 (51.4)1.2 (0.9–1.6)
 ≥1590 (19.2)96 (21.1)1.2 (0.8–1.7)102 (17.3)1.0 (0.7–1.4)
P for trend0.4260.903
Bra cup size 1 year before the reference date
 A17 (3.7)34 (7.6)1.9 (1.0–3.6)43 (7.4)1.8 (1.0–3.3)
 B152 (32.7)144 (32.1)Ref203 (34.9)Ref
 C166 (35.7)157 (35.0)1.0 (0.7–1.3)176 (30.3)0.8 (0.6–1.1)
 D or above130 (28.0)113 (25.2)0.9 (0.7–1.3)159 (27.4)0.9 (0.7–1.3)
P for trend0.1380.095

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.