Premenopausal serum androgens and breast cancer risk: a nested case-control study

Breast Cancer Research

Table 1 Case and control subject characteristics

Characteristic	Case subjects (n= 356)	Control subjects (n= 683)	P-value^a
Age at enrollment, years			matched
34 to 40	77 (22%)	152 (22%)
40 to 44	118 (33%)	235 (35%)
45 to 49	110 (31%)	205 (30%)
≥50	51 (14%)	91 (13%)
Age at diagnosis, years
< 45	48 (14%)
45 to 49	99 (28%)
50 to 54	101 (28%)
≥55	108 (30%)
Menopausal status at index date			0.06^b
Premenopausal	152 (49%)	316 (52%)
Postmenopausal	161 (51%)	293(48%)
Missing	43	74
Age at menarche, years			0.49^c
< 12	87 (25%)	157 (23%)
12	97 (27%)	167 (25%)
13	108 (30%)	210 (31%)
> 13	64 (18%)	144 (21%)
Missing	0	5
Nulliparous (%)	142 (40%)	230 (34%)	0.04^b
Age at first full-term pregnancy, years			0.03^c
< 25	91 (44%)	238 (54%)
25 to 30	54 (26%)	122 (27%)
30 to 34	41 (20%)	60 (14%)
≥35	21 (10%)	24 (5%)
Missing	7	9
First-degree family history of breast cancer (%)			0.004^b
No	264 (74%)	550 (81%)
Yes, one relative ≥45 years-old	64 (18%)	106 (15%)
Yes, one relative < 45 years-old or more than one relative	28 (8%)	27 (4%)
History of breast biopsy (%)	79 (22%)	127 (19%)	0.11^b
Ever use of oral contraceptives (%)	175 (56%)	362 (59%)	0.37^b
Missing	42	67
Body mass index (kg/m²)			0.19^c
< 20	55 (16%)	70 (10%)
20 to 22.4	111 (31%)	233 (34%)
22.5 to 24.9	79 (22%)	164 (24%)
25 to 29.9	76 (21%)	149 (22%)
≥30	34 (10%)	66 (10%)
Missing	1	1
Menstrual cycle regularity and number of periods in six months prior to blood donation			0.64^b
Irregular cycles	78 (23%)	139 (21%)
Regular cycles
< 5 cycles in 6 months	3 (1%)	8 (1%)
5 to7 cycles in 6 months	259 (76%)	516 (78%)
> 7 cycles in 6 months	2	2
Missing	14	18

^aBased on conditional logistic regression.^bP-value for unordered categorical variable, except for family history of breast cancer (ordered categorical variable). ^cP-value for variable on the continuous scale.

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