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Table 1 Case and control subject characteristics

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

Characteristic Case subjects
(n= 356)
Control subjects
(n= 683)
P-valuea
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    0.06b
   Premenopausal 152 (49%) 316 (52%)  
   Postmenopausal 161 (51%) 293(48%)  
   Missing 43 74  
Age at menarche, years    0.49c
   < 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%) 0.04b
Age at first full-term pregnancy, years    0.03c
   < 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 (%)    0.004b
   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%) 0.11b
Ever use of oral contraceptives (%) 175 (56%) 362 (59%) 0.37b
   Missing 42 67  
Body mass index (kg/m2)    0.19c
   < 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    0.64b
   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  
  1. 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.