Table 2: Breast cancer risk factors for the case and control subjects*
Risk factor	Group; no. (and %) of subjects		OR (and 95% CI)	p value
	Case	Control
Age at menarche, yr
>= 13	119 (54)	1329 (61)	1.00 RV
<= 12	101 (46)	854 (39)	1.32 (0.99–1.75)	0.051
Age at first live birth
<= 29 years	156 (71)	1647 (75)	1.00 RV
>= 30 years or nulliparous	64 (29)	546 (25)	1.24 (0.91–1.68)	0.17
No. of births
0	39 (18)	320 (15)	1.00 RV
1	27 (12)	192 (9)	1.17 (0.69–1.98)	0.56
>= 2	151 (70)	1668 (77)	0.74 (0.51–1.08)	0.12
Age at menopause, yr†
<= 44	29 (17)	446 (27)	1.00 RV
>= 45	139 (83)	1208 (73)	1.79 (1.18–2.71)	0.01
Hysterectomy
No	163 (74)	1466 (67)	1.00 RV
Yes	57 (26)	729 (33)	0.69 (0.50–0.96)	0.03
Oophorectomy
No	194 (90)	1881 (87)	1.00 RV
Yes	22 (10)	270 (13)	0.78 (0.49–1.24)	0.29
Oral contraceptive use
Never	105 (48)	972 (44)	1.00 RV
Ever	115 (52)	1224 (56)	0.86 (0.64–1.15)	0.30
Estrogen use
Never	152 (70)	1482 (68)	1.00 RV
Ever	64 (30)	696 (32)	0.88 (0.64–1.22)	0.45
Family history of breast cancer
No	121 (55)	1464 (67)	1.00 RV
Yes	99 (45)	733 (33)	1.63 (1.23–2.16)	0.001
Previous breast problem
No	177 (82)	1789 (83)	1.00 RV
Yes	40 (18)	356 (17)	1.14 (0.79–1.64)	0.48
*Missing responses were excluded.  †Women aged less than 45 years at enrolment (49 case subjects and 490 control subjects) were excluded from analysis.

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