Bra Wearing Not Associated with Breast Cancer Risk: A Population-Based Case–Control Study

Lu Chen; Kathleen E. Malone; Christopher I. Li

doi:10.1158/1055-9965.EPI-14-0414

DOI: 10.1158/1055-9965.EPI-14-0414 Published October 2014

Article Figures & Data

Tables

Table 1.

Distribution of selected characteristics among controls, ductal cases, and lobular cases

	Controls	Ductal cases	Lobular cases
	(n = 469)	(n = 454)	(n = 590)
Characteristic	n (%)	n (%)	n (%)
Age, y
55–59	137 (29.2)	126 (27.8)	178 (30.2)
60–64	121 (25.8)	109 (24.0)	155 (26.3)
65–69	113 (24.1)	117 (25.8)	141 (23.9)
70–74	98 (20.9)	102 (22.5)	116 (19.7)
Race/ethnicity
Non-Hispanic White	423 (90.2)	406 (89.6)	546 (92.5)
African American	8 (1.7)	10 (2.2)	9 (1.5)
Asian/Pacific Islander	9 (1.9)	16 (3.5)	11 (1.9)
Native American	10 (2.1)	11 (2.4)	11 (1.9)
Hispanic White	19 (4.1)	10 (2.2)	13 (2.2)
Missing	0	1	0
Education
High school or less	150 (32.0)	154 (33.9)	188 (31.9)
Some college	182 (38.8)	163 (35.9)	198 (33.6)
College graduates	87 (18.6)	88 (19.4)	124 (21.0)
Postgraduates	50 (10.7)	49 (10.8)	80 (13.6)
Annual income
<$20,000	38 (9.6)	54 (14.1)	62 (12.5)
$20,000–34,999	76 (19.3)	72 (18.8)	106 (21.4)
$35,000–69,999	159 (40.4)	136 (35.5)	160 (32.3)
$70,000–89,999	47 (11.9)	44 (11.5)	78 (15.7)
≥$90,000	74 (18.8)	77 (20.1)	90 (18.1)
Missing	75	71	94
BMI at 30 years of age (kg/m²)
<25.0	378 (82.0)	369 (81.8)	504 (86.7)
25.0–29.9	66 (14.3)	68 (15.1)	58 (10.0)
≥30.0	17 (3.7)	14 (3.1)	19 (3.3)
Missing	8	3	9
BMI 1 month before reference date (kg/m²)
<25.0	146 (31.2)	158 (34.8)	212 (36.1)
25.0–29.9	163 (34.8)	144 (31.7)	195 (33.2)
≥30	159 (34.0)	152 (33.5)	180 (30.7)
Missing	1	0	3
Menopausal hormone therapy use
Never	118 (25.3)	141 (31.2)	125 (21.2)
Former	107 (23.0)	70 (15.5)	81 (13.8)
Current estrogen only	146 (31.3)	110 (24.3)	142 (24.1)
Current estrogen + progestin	95 (20.4)	131 (29.0)	241 (40.9)
Missing	3	2	1
First-degree family history of breast cancer
No	380 (84.3)	334 (77.9)	440 (76.5)
Yes	71 (15.7)	95 (22.1)	135 (23.5)
Missing	18	25	15
Had a mammogram within the past 2 years
No	51 (10.9)	37 (8.1)	44 (7.5)
Yes	418 (89.1)	417 (91.9)	546 (92.5)
Menopausal status
Natural	266 (58.0)	302 (67.7)	391 (68.2)
Induced^a	68 (14.8)	49 (11.0)	71 (12.4)
Simple hysterectomy	125 (27.2)	95 (21.3)	111 (19.4)
Missing	10	8	17
Parous
No	36 (7.7)	60 (13.2)	81 (13.7)
Yes	433 (92.3)	394 (86.8)	509 (86.3)

↵^aWomen who had bilateral oophorectomy were classified as having an induced menopause.

Table 2.

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