Table 1.

Characteristics of Polish Breast Cancer Study participants (n = 4,194)

Characteristic	Case		Control		P valuea
	Number	Percentage	Number	Percentage
Age
Less than 40 years	80	4	92	4
40-49 years	501	26	554	25
50-59 years	668	34	759	34
60-69 years	508	26	588	26
At least 70 years	208	11	236	11
Menopausal status
Premenopausal	521	27	686	31	<0.01
Postmenopausal	1,444	73	1,543	69
Parity
Nulliparous	283	14	248	11	<0.01
Parous	1,682	86	1,981	89
Breastfeedingb
0 months	353	21	368	19	0.03
Less than 12 months	939	56	1,078	54
12 to 23 months	255	15	336	17
At least 24 months	135	8	199	10
Age at menarche
Not more than 12 years	562	29	497	23	<0.01
13 years	427	22	516	23
14 years	520	27	615	28
15 years	208	11	253	11
At least 16 years	233	12	322	15
Body mass index
Less than 25 kg/m2	732	37	705	32	<0.01
25 to less than 30 kg/m2	696	35	812	36
At least 30 kg/m2	535	27	709	32
Oral HT usec
Never	1,106	82	1,284	88	<0.01
Current	120	9	68	5
Recent	64	5	25	2
Past	62	5	83	6
Alcohol drinks per week
Never drinker	1,254	65	1,464	67	0.11
0 to less than 1	184	10	206	9
1 to less than 3	282	15	289	13
3 to less than 5	71	4	97	4
At least 5	137	7	121	6
Family history of breast cancerd
No	1,766	90	2,101	94	<0.01
Yes	198	10	128	6

^aPearson chi-square test P value. ^bParous women only. ^cHT, hormone therapy, postmenopausal women only. ^dMother, sister, daughter, excludes half-sisters.