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Table 1 Study population characteristics

From: Searching for early breast cancer biomarkers by serum protein profiling of pre-diagnostic serum; a nested case-control study

  Cases
(n = 68)
Controls
(n = 68)
P-value††
Age at enrollment (years)    
   Mean (SD) 60.2 (5.6) 60.3 (5.7) 0.966
BMI    
   Mean (SD) 26.6 (3.1) 26.3 (3.6) 0.603
   Missing 1 -  
Use of oral contraceptives, n (%)    
   No, but used to in the past 36 (52.9) 40 (58.8) 0.490
   No, never 32 (47.1) 28 (41.2)  
Duration of oral contraceptives use* (years)    
   Median (IQR) 10.0 (4.3-15.8) 4.5 (2.0-10.0) 0.018
Use of HT, n (%)    
   No, but used to in the past 7 (10.3) 6 (8.8) 0.771
   No, never 61 (89.7) 62 (91.2)  
Duration of HT use* (years)    
   Median (IQR) 1.0 (1.0-8.0) 2.0 (1.0-10.0) 0.273
Ovariectomy, n (%)    
   Both ovaries removed 5 (7.4) 3 (4.5) 0.479
   Missing - 1  
Parity, n (%)    
   Nulliparous 10 (14.7) 5 (7.4) 0.171
Number of children    
   Median (IQR) 2.0 (2.0-3.0) 3.0 (2.0-3.0) 0.100
Smoking, n (%)    
   No, but used to in the past 31 (45.6) 34 (50.0) 0.607
   No, never 37 (54.4) 34 (50.0)  
Pack-years smoking until stop date    
   Median (IQR) 7.9 (1.9-16.4) 4.1 (1.4-10.2) 0.187
   Missing 1 3  
Alcohol intake (g/day)§    
   Median (IQR) 2.0 (0.2-7.2) 2.5 (0.2-8.4) 0.638
Use of medicines, minerals or vitamins #, n (%)    
   Yes 46 (67.6) 44 (64.7)  
   No 22 (32.4) 24 (35.3) 0.717
Time since last meal and/or drink** (min)    
   Median (IQR) 108 (87-137) 116 (88-137) 0.651
  1. SD: standard deviation; BMI: body mass index; IQR: inter-quartile range; HT: menopausal hormone therapy; * Among former oral contraceptives/HT users; Among women with children; Among former smokers; § Energy-adjusted alcohol intake at enrollment; # In last week before blood collection; ** At moment of blood collection; †† Independent samples T test for age and BMI, Mann-Whitney U test for other continuous variables, and Pearson Chi-Square test for categorical variables.