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Table 1 Distribution of background factors in postmenopausal women diagnosed with breast cancer in relation to age at menarche

From: The influence of menstrual risk factors on tumor characteristics and survival in postmenopausal breast cancer

  Age at menarche, years P valuea
  ≤ 11 > 11 and ≤13 > 13 and ≤14 > 14  
  Column frequency, number (percentage)  
Total number of cases (n = 2,640) 167 989 698 542  
Background factors      
Menstrual cycle length, days      
   ≤27.5 35 (30) 183 (26) 125 (26) 93 (26)  
   28 64 (55) 392 (55) 258 (54) 191 (54)  
   > 28 17 (15) 136 (19) 96 (20) 71 (20) 0.877
Irregular menstruation      
   No 159 (96) 39 (4) 18 (3) 518 (98)  
   Yes 7 (4) 940 (96) 672 (97) 13 (2) 0.246
Age at first birth, years      
   < 25 73 (51) 418 (50) 268 (45) 226 (49)  
   ≥25 and < 30 44 (31) 281 (34) 200 (34) 149 (32)  
   ≥30 27 (19) 136 (16) 129 (21) 86 (19) 0.240
Parity      
   0 23 (14) 154 (16) 101 (14) 81 (15)  
   1 30 (18) 215 (21) 154 (22) 105 (19)  
   2 68 (41) 362 (37) 269 (39) 215 (40)  
   3+ 46 (28) 258 (26) 174 (25) 141 (26) 0.893
Pregnancy terminated < 6 months, nulliparous      
   No 7 (88) 15 (38) 18 (49) 9 (45)  
   Yes 1 (12) 25 (62) 19 (51) 11 (55) 0.079
Pregnancy terminated < 6 months, parous      
   No 100 (71) 631 (76) 431 (73) 363 (79)  
   Yes 40 (29) 197 (24) 160 (27) 95 (21) 0.069
Age at menopause, yearsb      
   < 50 45 (31) 261 (31) 198 (34) 133 (28)  
   50–55 86 (59) 520 (62) 344 (58) 299 (63)  
   > 55 14 (10) 55 (7) 47 (8) 43 (9) 0.312
Ever use of MHTc      
   No 105 (63) 646 (66) 483 (69) 370 (68)  
   Yes 61 (37) 340 (34) 215 (31) 171 (32) 0.258
MHT use by general type      
   Exclusive estrogen use 14 (9) 67 (7) 54 (8) 39 (8)  
   Estrogen-progestin combined use 39 (25) 233 (25) 142 (21) 111 (21) 0.566
Diagnosed via mammographic screening      
   Screening 102 (61) 546 (56) 399 (58) 301 (57)  
   Other 64 (39) 436 (44) 288 (42) 228 (43) 0.484
Deceased at end of 5-year follow-up 27 (16) 134 (14) 101 (15) 74 (14) 0.802
Breast cancer deaths at end of 5-year follow-up (total = 264) 23 (14) 89 (9) 71 (10) 46 (8) 0.186
  1. aPearson chi-square tests of association between groups. bAmong women with a natural known menopause. cMenopausal hormone therapy includes all treatments: exclusive estrogens, exclusive progestins, and combined estrogen-progestin therapy.