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Table 1 Demographic and reproductive health characteristics of women with breast cancer (cases) and controls by study

From: Body size in early life and risk of breast cancer

   KARMA LIBRO1
Variables Categories Cases (n = 2272) Controls (n = 10,468) P value* Cases (n = 4459) Controls (n = 18237) P value*
Demographics
 Age at questionnaire, years Mean ± SD 61.3 ± 9.2 55.7 ± 9.2 <0.001 62.6 ± 9.7 57.4 ± 9.1 <0.001
 Body size at age 7 years, n (%) Small 1327 (58.4) 5644 (53.9) <0.001 2727 (61.2) 9870 (54.1) <0.001
Medium 773 (34.0) 3824 (36.5) 1358 (30.5) 6622 (36.3)
Large 172 (7.6) 1000 (9.6) 374 (8.4) 1745 (9.6)
 Body size at age 18 years, n (%) Small 705 (31.0) 3042 (29.1) 0.001 1482 (33.3) 5233 (28.7) <0.001
Medium 1407 (61.9) 6433 (61.5) 2638 (59.2) 11,135 (61.1)
Large 160 (7.0) 992 (9.5) 334 (7.5) 1866 (10.2)
 BMI at questionnaire, kg/m2 Mean ± SD 25.6 ± 4.2 25.2 ± 4.1 <0.001 25.3 ± 4.2 25.2 ± 4.2 0.071
Reproductive health factors
 Age at menarche, years Mean ± SD 13.2 ± 1.5 13.2 ± 1.5 0.735 13.1 ± 1.5 13.1 ± 1.5 0.398
 Number of children, n (%) Nulliparous 407 (13.1) 1574 (11.8) 0.018 673 (15.1) 2599 (14.3) <0.001
1 502 (16.1) 1910 (14.3) 790 (17.7) 2746 (15.1)
2 1463 (46.9) 6425 (48.2) 1975 (44.3) 8425 (46.2)
≥3 743 (23.9) 3430 (25.7) 1021 (22.9) 4467 (24.5)
 Menopause status, n (%) Postmenopause 1999 (87.9) 6733 (64.3) <0.001 4229 (94.8) 13,143 (72.1) <0.001
Premenopause 273 (12.0) 3735 (35.7) 230 (5.2) 5094 (27.9)
 Ever used HRT, n (%) Yes 882 (38.8) 3025 (28.9) <0.001 2381 (53.4) 6225 (34.1) <0.001
No 1390 (61.2) 7443 (71.1) 2078 (46.6) 12,012 (65.9)
 Family history of breast cancer, n (%) Yes 487 (21.4) 1431 (13.7) <0.001 900 (20.2) 2426 (13.3) <0.001
No 1785 (78.6) 9037 (86.3) 3559 (75.4) 15,811 (86.7)
  1. SD standard deviation, BMI body mass index, HRT hormone replacement therapy. *P values were derived from chi-square tests for categorical variables and from the independent sample t test for continuous variables