A Matched Case-Control Study of Risk Factors for Breast Cancer Risk in Vietnam

Table 5

Conditional logistic regression analysis to estimate the odds (odd ratio, OR) of breast cancer in premenopausal women.

	Cases	Controls	Unadjusted OR			Adjusted OR
			OR	95% CI		OR	95% CI
Reproductive factors
Age at menarche	15.8	15.7	1.03	0.92–1.14	0.64	1	0.89–1.15	0.84
0	10 (5.3%)	4 (2.1%)	1			1
1	16 (8.2%)	7 (3.6%)	0.83	0.17–4.05	0.82	1.25	0.24–6.63	0.05
2	110 (56.1%)	96 (49.0%)	0.38	0.10–1.47	0.16	0.43	0.11–1.72	0.47
3	39 (19.9%)	64 (32.7%)	0.19	0.05–0.74	0.02	0.22	0.05–0.95	0.004
4+	14 (7.1%)	24 (12.2%)	0.25	0.06–1.09	0.06	0.28	0.06–1.26	0.09
Age at 1st parity	24.2	23.7	1.03	0.97–1.09	0.33
Total months breastfeeding	36.1	37.4	1	0.99–1.02	0.81
Anthropometric factors
BMI at age
<18 kg/m^2	42 (21.5%)	60 (31.6%)	1			1
18–20 kg/m^2	64 (32.8%)	80 (42.1%)	1.16	0.69–1.94	0.44	1.33	0.76–2.34	0.24
>20 kg/m^2	89 (45.6%)	50 (26.3%)	2.73	1.56–4.79	0.0006	2.801	1.51–5.20	0.001
Hormonal factors
OCP
No	173 (89.2%)	184 (94.9%)	1			1
Yes	21 (10.8%)	10 (5.2%)	2.2	1.01–4.89	0.05	2.11	0.89–5.01	0.09

denotes the variables used for multivariate analysis to calculate the adjusted OR.