Table 3.

Odds ratios (ORs) and 95% confidence intervals (CIs) associated with reproductive factors and inflammatory (IBC) and non-IBC

Variable	IBC (N= 267)	Non-IBC (N=274)	Control (N= 275)	IBC vs. controls OR (95% CI)a	Non-IBC vs. Controls OR (95% CI)a
Age at Menarche
<12	30	42	22	1.8 (0.9–3.6)	2.1 (1.0–4.2)
12–13	120	118	142	1.0	1.0
≥14	76	87	86	1.0 (0.7–1.5)	1.2 (0.8–1.8)
Unknown	41	27	25
Number of livebirths
1–2	55	67	68	1.0	1.0
3–4	97	98	102	1.2 (0.8–1.9)	0.9 (0.6–1.4)
≥5	74	61	50	1.9 (1.1–3.3)	1.1 (0.7–1.9)
Nulliparous	41	48	55	1.0 (0.6–1.6)	0.9 (0.5–1.5)
Age at first livebirth, years
< 20	58	54	45	1.0	1.0
20–24	72	89	76	0.7 (0.4–1.2)	0.9 (0.6–1.5)
≥25	95	81	98	0.7 (0.4–1.2)	0.6 (0.4–1.1)
Nulliparous	41	48	55	0.6 (0.3–1.0)	0.7 (0.4–1.3)
Unknown	1	2	1
Age at last livebirth, years
<30	53	71	72	1.0	1.0
30–34	72	72	80	1.2 (0.4–1.9)	0.9 (0.6–1.4)
≥35	100	81	66	2.1 (1.3–3.9)	1.2 (0.8–2.0)
Nulliparous	41	48	55	1.1 (0.6–1.8)	0.9 (0.6–1.6)
Unknown	1	2	1
Time since last live birth, years
≥10	148	171	164	1.0	1.0
5–9	29	31	30	1.4 (0.8–2.7)	1.1 (0.6–1.9)
3–4	20	10	13	2.7 (1.2–6.0)	0.8 (0.3–2.1)
0–2	28	12	11	4.5 (1.9–10.3)	1.1 (0.5–2.9)
Nulliparous	41	48	55	1.0 (0.6–1.6)	0.9 (0.6–1.5)
Unknown	1	2	1
Duration breast feeding (months) -among parous women who breast fed
0 – < 24	31	41	35	1.0	1.0
24 – < 60	68	85	76	1.1 (0.6–2.0)	1.0 (0.6–1.7)
60 – < 84	41	33	45	1.2 (0.6–2.4)	0.7 (0.3–1.4)
≥84	57	49	33	2.4 (1.2–4.9)	1.3 (0.6–2.6)
Unknown	12	6	19
Never breast fed-parous	17	12	12	1.8 (0.7–4.4)	1.0 (0.4–2.7)
Unknown whether breast fed			1
Nulliparous	41	48	55	1.0 (0.5–1.8)	0.9 (0.5–2.6)
Duration exclusive breast feeding (months) among parous women who breast fed
0 – < 12	43	59	53	1.0	1.0
12 – < 24	65	72	74	1.4 (0.9–2.4)	1.0 (0.6–1.7)
24 – < 36	45	44	33	2.4 (1.3–4.4)	1.4 (0.8–2.4)
≥ 36	35	22	21	3.1 (1.6–6.1)	1.1 (0.6–2.3)
Unknown	21	17	27
Never breast fed-parous	17	12	12	2.2 (1.0–5.2)	1.2 (0.5–2.8)
Unknown whether breast fed			1
Nulliparous	41	48	55	1.2 (0.7–2.1)	1.0 (0.6–1.7)
Ever had a breast problemb that prevented lactation, occurred during lactation or within 6 months after stopping lactation
No	233	256	266	1.0	1.0
Yes	34	18	9	4.4 (2.1–9.6)	2.1 (0.9–4.8)
Didn’t breast feed or stopped because of insufficient milk
No among parous	184	192	180	1.0	1.0
Yes	42	34	39	1.0 (0.6–1.7)	0.8 (0.5–1.3)
Nulliparous	41	48	55	0.8 (0.5–1.2)	0.9 (0.6–1.4)
Ever tried to get pregnant for 2 years and/or visited a doctor for infertility
No	229	247	241	1.0	1.0
Yes	38	27	34	1.2 (0.7–1.9)	0.8 (0.4–1.3)
Years of oral contraceptive use (yrs)
No use	156	164	186	1.0	1.0
< 5	45	46	28	2.0 (1.2–3.5)	2.0 (1.3–2.4)
5–9	31	20	18	2.3 (1.2–4.3)	1.4 (0.7–2.9)
≥10	35	44	43	1.1 (0.6–1.8)	1.3 (0.8–2.1)
Age at first oral contraceptive use
Never	156	164	186	1.0	1.0
<25	40	55	35	1.5 (0.9–2.5)	2.1 (1.2–3.4)
25–34	52	37	48	1.4 (0.9–2.2)	0.9 (0.6–1.5)
≥ 35	19	18	6	4.1 (1.6–10.6)	3.8 (1.4–9.9)
Age last first oral contraceptive use
Never	156	164	184	1.0	1.0
<30	24	26	17	1.8 (0.9–3.5)	1.9 (1.0–3.7)
30–39	43	34	35	1.6 (1.0–2.7)	1.2 (0.7–2.0)
≥ 40	44	50	37	1.6 (0.9–2.6)	1.7 (1.1–2.8)

^aBased on multiply imputed data; frequencies are before imputation; adjusted for matching variables: age categories (20–29, 30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–84) as continuous, and location as shown in table 1.

^bAbscess, ulcer/sore, secretions, redness, swelling, pain, sore nipples, other