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Table 1 Comparison of cases and controls on demographics and potential confounding factors, NECSS, Canada, 1994-1997

From: Antioxidants and breast cancer risk- a population-based case-control study in Canada

  Premenopausal Postmenopausal
Characteristic Cases (N = 866) Controls (N = 845) P Cases(1496) Controls (n = 1617) P
Age (mean ± SD) 44.8 ± 6.2 43.8 ± 7.6 0.003 62.0 ± 8.5 62.7 ± 8.1 0.03
Education (years) (mean ± SD) 13.5 ± 3.1 13.6 ± 3.3 0.51 11.7 ± 3.4 11.3 ± 3.5 0.0009
Smoking pack-years (mean ± SD) 5.9 ± 9.4 5.8 ± 9.4 0.72 10.5 ± 15.0 8.8 ± 14.4 0.001
Alcohol consumption (drinks/wk) (mean ± SD)) 2.9 ± 5.7 2.7 ± 5.1 0.48 3.1 ± 6.7 2.5 ± 5.6 0.01
BMI (kg/m2 ) (mean ± SD) 24.7 ± 5.2 24.5 ± 4.8 0.29 26.1 ± 5.9 25.7 ± 5.5 0.03
Moderate physical Activity (frequency/month (mean ± SD)) 15.9 ± 14.9 15.7 ± 14.1 0.67 18.6 ± 15.4 18.0 ± 15.9 0.28
Strenuous physical activity (frequency/month (mean ± SD)) 4.8 ± 8.4 4.9 ± 8.0 0.77 3.3 ± 7.8 3.5 ± 8.1 0.42
Total energy intake (kcals/week) 12915 ± 4791 12687 ± 5440 0.35 12965 ± 5333 12775 ± 6997 0.39
Years of menstruation (mean ± SD) 32.0 ± 6.2 30.9 ± 7.7 0.001 33.0 ± 7.7 32.4 ± 7.6 0.02
Age at menarche (mean ± SD) 12.6 ± 1.4 12.8 ± 1.5 0.005 12.8 ± 1.6 13.0 ± 1.7 0.01
Marital status    0.89    < 0.0001
   Marred 659 621   1003 1057  
   Common law 51 44   19 27  
   Divorced/separated 74 97   136 129  
   Windowed 16 18   248 340  
   Single 60 59   86 59  
   Other 4 4   2 2  
No. live birth    0.27    < 0.0001
   0- 162 168   230 174  
   1- 118 107   153 143  
   2- 366 330   400 395  
   3- 162 146   338 319  
   ≥ 4 56 93   372 581  
Family income adequacy    0.05    0.17
   Low 102 111   283 306  
   Low middle 146 138   234 276  
   Upper middle 274 259   302 317  
   High 202 155   217 199  
Smoking status    0.72    0.006
   Never 409 413   697 826  
   Ex-smoker 267 221   488 505  
   Current smoker 190 211   311 286