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Table 2 Associations of coffee consumption and breast cancer risk factors in Swedish study (controls only)

From: Coffee consumption modifies risk of estrogen-receptor negative breast cancer

Breast cancer risk factors Daily coffee consumption  
  ≤ 1 cup 2 to 3 cups 4 to 5 cups > 5 cups Ptrenda
Age at menarche, continuous (y)      
Mean (SD) 13.5 (1.5) 13.6 (1.4) 13.6 (1.4) 13.6 (1.5) 0.506
Controls (n) in each coffee consumption category 246 1,054 776 326  
Age at menopause, continuous (y)      
Mean (SD) 49.9 (4.1) 50 (4.1) 50 (3.8) 50.2 (3.6) 0.331
Controls (n) in each coffee consumption category 268 1,164 840 360  
Body mass index, continuous (kg/m2)      
Mean (SD) 25.4 (5.1) 25.4 (4) 25.4 (4) 25.4 (4.7) 0.979
Controls (n) in each coffee consumption category 264 1,158 840 362  
Alcohol consumption (g/day)      
Mean (SD) 2.1 (4.2) 2.2 (4.0) 2 (3.7) 2 (4.3) 0.411
Controls (n) in each coffee consumption category 252 1,056 761 327  
Hormone replacement therapy      
Proportion of ever users 0.46 0.44 0.42 0.37 0.008
  269 1,160 843 361  
Family history of breast cancer      
Proportion with family history of breast cancer 0.11 0.10 0.09 0.08 0.281
Controls (n) in each coffee consumption category 266 1,154 830 353  
Smoked > 1 year or > 100 cigarettes (No/Yes)      
Proportion of Yes 0.37 0.37 0.47 0.57 < 0.0001
Controls (n) in each coffee consumption category 270 1,170 846 363  
Parity/Age at first birth, categorical      
Proportion of nulliparous 0.14 0.12 0.09 0.10 0.876
Proportion of parous with age of first birth < 25 y 0.42 0.47 0.49 0.50  
Proportion of parous with age of first birth ≥ 25 y and < 30 y 0.30 0.30 0.26 0.29  
Proportion of parous with age of first birth ≥ 30 y 0.14 0.11 0.15 0.10  
Controls (n) in each coffee consumption category 270 1,171 846 363  
Education, categorical      
Proportion of highest education level      
to elementary school 0.39 0.52 0.50 0.50 0.041
- junior secondary school 0.25 0.22 0.23 0.24  
- high school 0.19 0.14 0.14 0.15  
- university 0.18 0.12 0.12 0.11  
Controls (n) in each coffee consumption category 269 1,168 843 362  
Physical activity one year before recruitment, categorical      
- none 0.17 0.19 0.16 0.22 0.624
- < 1 h per week 0.18 0.17 0.15 0.16  
- 1 to 2 h per week 0.31 0.31 0.34 0.26  
- > 2 h per week 0.35 0.33 0.36 0.36  
Controls (n) in each coffee consumption category 267 1,165 842 362  
  1. aTo obtain P-value for trend for coffee consumption treated as a continuous variable, linear regression analysis was performed for continuous risk factor variables (age at menarche (years), age at menopause (years), body mass index (kg/m2) and alcohol consumption (g/day)), logistic regression analysis was performed for binary risk factor variables (hormone replacement therapy, family history of breast cancer and smoking), and proportional odds logistic regression was performed for categorical risk factor variables (parity/age at first birth, highest education level, and physical activity one year before enrolment).
  2. SD, standard deviation; y, year(s).