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

Table 3

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

	Cases	Controls	Unadjusted OR			Adjusted OR
			OR	95% CI		OR	95% CI
Reproductive factors
Age at menarche	15.8	16	0.94	0.86–1.03	0.16	0.95	0.86–1.05	0.28
0	14 (4.9%)	5 (1.7%)	1			1
1	29 (9.8%)	17 (5.8%)	0.5	0.15–1.72	0.27	0.5093	0.14–1.75	0.19
2	150 (51.0%)	123 (41.8%)	0.34	0.11–1.10	0.07	0.33	0.10–1.09	0.81
3	62 (21.1%)	98 (33.3%)	0.18	0.05–0.58	0.004	0.17	0.05–0.59	0.001
4+	30 (10.2%)	49 (16.7%)	0.16	0.04–0.55	0.004	0.17	0.05–0.63	0.008
Age at 1st parity	24.5	23.8	1.05	1.00–1.10	0.06
Total months breastfeeding	35.7	37.6	1	0.99–1.02	0.91
Anthropometric factors
BMI at age
<18 kg/m^2	65 (22.2%)	75 (26.2%)	1			1
18–20 kg/m^2	98 (33.6%)	124 (43.4%)	0.9188	0.59–1.38	0.36	1.0072	0.63–1.57	0.23
>20 kg/m^2	130 (44.4%)	87 (30.4%)	1.79	1.16–2.78	0.0011	1.72	1.07–2.76	0.003
Hormonal factors
OCP
No	266 (91.4%)	278 (95.5%)	1			1
Yes	25 (8.6%)	13 (4.5%)	2	1.00–4.00	0.05	2.03	0.94–4.42	0.07
Menopause
No	196 (74.5%)	218 (76.2%)	1
Yes	67 (25.5%)	68 (23.8%)	1.04	0.61–1.76	0.89

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