Skip to main content

Table 1 Case–control status and distribution of potential confounders

From: Genetic predisposition, parity, age at first childbirth and risk for breast cancer

Factor Category Case (n = 728) Control (n = 1448)
   Column% (n) Mean (SD) in italics 
Education O-level college 67.9 (494) 70.2 (1017)
  A-level college 7.1 (52) 7.0 (101)
  University 24.7 (180) 22.4 (325)
  Missing 0.3 (2) 0.3 (5)
Type of occupation Manual worker 33.2 (242) 38.5 (557)
  Non-manual worker 60.0 (437) 52.3 (757)
  Employer-self-employed 5.5 (40) 8.1 (118)
  Missing 1.2 (9) 1.1 (16)
Married/cohabiting No 33.7 (245) 33.4 (483)
  Yes 66.3 (483) 66.6 (965)
  Missing --- ---
Age at menarche ≤12 20.9 (152) 21.4 (310)
  >12 to <15 52.2 (380) 53.8 (779)
  ≥15 26.0 (189) 23.8 (344)
  Missing 1.0 (7) 1.0 (15)
Parity Nullipara 11.5 (84) 9.7 (141)
  1 19.8 (144) 21.3 (309)
  2 44.6 (325) 41.9 (607)
  ≥3 21.6 (157) 24.8 (359)
  Missing 2.5 (18) 2.2 (32)
Age at first childbirth Nullipara 11.5 (84) 9.7 (141)
  ≤20 15.5 (113) 16.2 (234)
  >20 to ≤25 34.8 (253) 36.3 (526)
  >25 to ≤30 25.5 (186) 26.7 (387)
  >30 10.2 (74) 8.8 (127)
  Missing 2.5 (18) 2.3 (33)
Bilateral oophorectomy No 98.9 (720) 98.3 (1424)
  Yes 1.1 (8) 1.7 (24)
  Missing --- ---
  Pre-/Perimenopausal 33.3 (482) 34.6 (252)
Age at menopause ≤45 11.9 (172) 11.5 (84)
  >45 to <53 39.2 (567) 37.4 (272)
  ≥53 14.4 (209) 14.3 (104)
  Missing 1.2 (18) 2.2 (16)
Exposure to OC (ever/never) No 46.8 (341) 49.0 (709)
  Yes 53.0 (386) 50.8 (735)
  Missing 0.1 (1) 0.3 (4)
Exposure to HRT (current/non) No, pre menopausal 23.0 (167) 21.1 (306)
  No, peri-/post menopausal 49.3 (359) 59.4 (860)
  ERT 5.1 (37) 6.3 (91)
  PRT 1.2 (9) 0.5 (7)
  CHRT 21.2 (154) 12.3 (178)
  Missing 0.3 (2) 0.4 (6)
Height Mean (standard deviation) 164.3 (5.8) 163.8 (6.0)
  Missing for both cases and controls   
Body mass index Mean (standard deviation) 25.6 (4.1) 25.5 (4.4)
  Missing for both cases and controls   
Alcohol consumption Nothing last year (teetotaler) 10.2 (74) 12.0 (174)
  Something last year (not last month) 10.6 (77) 12.1 (175)
  Something last month 79.0 (575) 75.6 (1094)
  Missing 0.3 (2) 0.3 (5)
Smoking Never 43.4 (316) 43.2 (626)
  Current 27.5 (200) 28.1 (407)
  Ex 29.1 (212) 28.5 (413)
  Missing 0.0 (0) 0.1 (2)