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Table 4 Breast cancer-specific five-year survival in relation to menstrual factors

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

Menstrual factors Deaths Mortality ratea Hazard ratio (95% CI)b
Age at menarch, yearsc    
   > 14 46 1.81 1.00 (reference)
   > 13 and ≤14 71 2.19 1.26 (0.86–1.84)
   > 11 and ≤13 89 1.93 1.14 (0.79–1.65)
   ≤11 23 2.99 1.72 (1.02–2.89)
Irregular menstruation    
   No 253 2.16 1.00 (reference)
   Yes 7 1.77 0.91 (0.43–1.93)
Cycle length, days    
   ≤27.5 39 1.79 1.00 (reference)
   28 95 2.16 1.15 (0.78–1.68)
   > 28 29 1.78 0.98 (0.60–1.61)
Total lifetime menstrual cycles, number    
   ≤423 58 2.10 1.00 (reference)
   > 423 and ≤500 104 2.00 0.99 (0.71–1.38)
   > 500 57 2.09 1.04 (0.72–1.52)
Age at menopause, years    
   < 50 79 2.43 1.00 (reference)
   50–55 138 2.18 0.92 (0.69–1.22)
   > 55 17 2.22 1.04 (0.60–1.80)
  1. aBreast cancer deaths per 100 person-years. bAll menstrual factor hazard ratio estimates adjusted for age at first birth, age at diagnosis, ever use and type of menopausal hormone therapy (never users, exclusive estrogen therapy, and combined estrogen-progestin therapy).cAge at menarche hazard ratio estimates additionally adjusted for body mass index at 18 years of age.