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Table 1 Distribution of demographic and established risk factors for breast cancer in cancer patients (cases) and control subjects, The Singapore Chinese Health Study, 1993 to 1998

From: Breast cancer risk assessment using genetic variants and risk factors in a Singapore Chinese population

  Cases (n = 411) Controls (n = 1,212) P *
Demographic factors
Mean age, years (SD) 54.9 (7.6) 54.9 (7.5) 0.964
Education level, n (%)    0.003
None 104 (25.3) 399 (32.9)
Primary 186 (45.3) 518 (42.7)
Secondary or higher 121 (29.4) 295 (24.3)
Reproductive risk factors
Number of live births, n (%)    <0.001
Nulliparous 56 (13.6) 85 (7.0)
1-2 146 (35.5) 369 (30.4)
3-4 131 (31.9) 483 (39.9)
5 or more 78 (19.0) 275 (22.7)
Mean age at first live birth, years (SD) 25.6 (4.9) 25.0 (4.7) 0.022
Mean age at menarche, years (SD) 14.1 (1.7) 14.3 (1.8) 0.033
Mean age at menopause, years (SD) 49.7 (4.4) 49.2 (4.3) 0.141
Estrogen use, n (%)    0.042
Non-user 372 (90.5) 1,131 (93.3)
Ex-user 8 (1.9) 22 (1.8)
Current user 31 (7.5) 59 (4.9)
Other risk factors
Family history of breast cancer, n (%)    0.063
No 400 (97.3) 1,196 (98.7)
Yes 11 (2.7) 16 (1.3)
History of past biopsy, n (%)    0.252
No 401 (97.6) 1,193 (98.4)
Yes 10 (2.4) 19 (1.6)
Mean body mass index, kg/m2 (SD) 23.5 (3.4) 23.2 (3.2) 0.066
Marine n-3 omega fatty acids, g (SD) 0.90 (0.4) 0.90 (0.5) 0.299
Vegetable-fruit-soy intake, n (%)    0.969
0 79 (19.2) 241 (19.9)
1 99 (24.1) 307 (25.3)
2 130 (31.6) 332 (27.4)
3 103 (25.1) 332 (27.4)
Green tea intake in tertiles, n (%)    0.418
None 234 (56.9) 713 (58.8)
First 77 (18.7) 219 (18.1)
Second 43 (10.5) 134 (11.1)
Third 57 (13.9) 146 (12.0)
Mean isoflavanoids, mg (SD) 19.4 (20.4) 19.8 (17.3) 0.700
Sleep duration, hours per day (SD) 7.0 (1.1) 7.0 (1.1) 0.685
Genetic risk score in quartiles, n (%)    
First (32.4 - 43.6) 80 (19.5) 326 (26.9) <0.001
Second (43.6 - 47.1) 96 (23.4) 310 (25.6)  
Third (47.1 - 50.6) 109 (26.5) 296 (24.4)  
Fourth (50.6 - 65.8) 126 (30.7) 280 (23.1)
  1. *Two-sided P values were derived from chi-squared test for categorical variables and t test for continuous variables; the Mantel-Haenszel chi-squared test for trend with one degree of freedom for categorical variables with more than two levels. SD, standard deviation.