Table 1.

Distribution of selected variables between breast cancer patients and control subjects

Variable	Cases (n = 926)		Controls (n = 1,187)		Pa
	N	%	N	%
Age at diagnosis (mean ± SD), years	52.2 ± 12.2		44.8 ± 12.5		<0.001
≤50	453	48.9	819	69.0	<0.001
>50	473	51.1	368	31.0
Age at menarche, years
≤13	144	15.6	229	19.3	<0.001
14 to 16	406	43.8	643	54.2
≥17	138	14.9	114	9.6
Not available	238	25.7	201	16.9
Childbearing history
0 children	26	2.8	132	11.1	<0.001
1 child	456	49.2	707	59.6
2 children	191	20.6	162	13.6
≥3 children	93	10.0	69	5.8
Not available	160	17.3	117	9.9
Family history
Yes	47	5.1	38	3.2	0.012
No	814	87.9	1143	96.3
Not available	65	7.0	6	0.5

^aStudent’s t test for age distribution between case and control groups; chi-square test for family history distribution between case and control groups; nonparametric rank test for other variables distribution between case and control groups.