Polymorphisms in estrogen-metabolizing and estrogen receptor genes and the risk of developing breast cancer among a cohort of women with benign breast disease

Table 2 Characteristics of the study cohort (n = 1438)

Characteristic	n	%
Race
Caucasian	1438	100.0
Age, years^a
<50	533	37.1
50 to 60	411	28.6
>60	494	34.3
Missing	0	0.0
Education, years^a
less than a high school degree	259	18.0
high school degree	714	49.7
some college	463	32.2
Missing	2	0.1
Menopausal status^a
Pre-menopausal	377	26.2
Peri-menopausal	35	2.4
Post-menopausal	995	69.2
Missing	31	2.2
Family history of breast cancer^a
No	715	49.7
Yes	275	19.1
Missing	448	31.2
Ever been pregnant (%)^b
No	176	12.2
Yes	1255	87.3
Missing	7	0.5
Age at first birth (years, %)^b
Nulliparous	176	12.2
20	347	24.1
20 to 24	539	37.5
≥25	339	23.6
Missing	37	2.6
Age at menarche (years, %)^b
<12	268	18.6
12 to 13	763	53.1
>13	386	26.8
Missing	21	1.5
Height, inches^a
<62	411	28.6
62–64	419	29.1
>64	608	42.3
Missing	0	0.0
Weight, pounds^a
<130	354	24.6
130–<145	318	22.1
145–<165	377	26.2
≥165	387	26.9
Missing	2	0.1
BMI, kg/m^{2, a}
<24.9	744	51.7
25.0 – 29.9	433	30.1
≥30	259	18.0
Missing	2	0.1
Smoking status^a
Never	839	58.3
Former	366	25.5
Current	232	16.1
Missing	1	0.1
Current alcohol drinker^a
No	814	56.6
Yes	413	28.7
Missing	211	14.7