Table 2 Cox proportional hazards regression analyses for the crude HR and multiple variable-adjusted HR for risk of breast cancer in women recruited before and after menopause

From: Body mass index and breast cancer: analysis of a nation-wide population-based prospective cohort study on 1 393 985 Taiwanese women

Factors

Pre-menopause

 

Post-menopause

 
 

Crude HR

aHR

Crude HR

aHR

 

(95% CI)

(95% CI)

P-value

(95% CI)

(95% CI)

P-value

BMI (vs 18.5–23.9)

 <18.5

0.94(0.82,1.07)

0.94(0.81,1.10)

0.9999a

0.79(0.65,0.97)

0.78(0.63,0.96)

<0.0001a

 24–26.9

0.95(0.90,1.01)

0.98(0.91,1.04)

 

1.13(1.06,1.20)

1.19(1.12,1.27)

 

 27–29.9

0.96(0.87,1.04)

1.02(0.93,1.13)

 

1.22(1.13,1.31)

1.31(1.21,1.41)

 

 30–34.9

0.93(0.81,1.06)

1.01(0.86,1.18)

 

1.41(1.27,1.56)

1.53(1.38,1.71)

 

 ⩾35

0.71(0.49,1.03)

0.82(0.54,1.24)b

 

1.50(1.17,1.92)

1.65(1.27,2.13)

 

Age at recruitment (vs <40)

 40–49

1.26(1.19,1.34)

1.39(1.30,1.48)

<0.0001a

1.11(0.61,2.03)

0.96(0.49,1.88)

<0.0001a

 50–59

1.39(1.29,1.49)

1.72(1.56,1.90)

 

1.34(0.74,2.42)

1.25(0.65,2.41)

 

 60–69

—

  

1.07(0.59,1.93)

1.21(0.63,2.33)

 

 ⩾70

—

  

0.59(0.33,1.08)

0.73(0.37,1.41)

 

Age at menarche (vs ⩽13)

 14

0.91(0.85,0.97)

0.96(0.90,1.03)

<0.0001a

0.88(0.82,0.95)

0.94(0.87,1.02)

<0.0001a

 15

0.83(0.83,0.89)

0.89(0.82,0.96)

 

0.83(0.77,0.90)

0.92(0.85,1.00)

 

 ⩾16

0.76(0.76,0.82)

0.82(0.76,0.89)

 

0.66(0.62,0.71)

0.78(0.72,0.84)

 

Birth (vs no)

 Yes

0.73(0.66,0.81)

0.81(0.62,1.06)

0.1186

0.62(0.56,0.69)

0.67(0.54,0.83)

0.0003

No. of birth c (vs 1)

 2

0.86(0.79,0.94)

0.91(0.82,1.00)

<0.0001a

0.89(0.79,1.01)

0.96(0.83,1.10)

<0.0001a

 ⩾3

0.66(0.60,0.71)

0.76(0.69,0.85)

 

0.59(0.53,0.66)

0.80(0.70,0.92)

 

Age at first full-term pregnancyc (vs ⩽22)

 23–25

1.29(1.20,1.39)

1.28(1.18,1.39)

<0.0001a

1.20(1.13,1.27)

1.15(1.08,1.23)

<0.0001a

 26–29

1.54(1.43,1.66)

1.46(1.35,1.58)

 

1.57(1.47,1.68)

1.33(1.23,1.44)

 

 ⩾30

1.89(1.74,2.06)

1.69(1.54,1.87)

 

1.87(1.72,2.05)

1.51(1.36,1.68)

 

Breast feeding c (vs no)

 Yes

0.86(0.82,0.91)

0.94(0.89,0.99)

0.0243

0.67(0.63,0.71)

0.86(0.80,0.92)

<0.0001

Family history (vs no)

 Yes

1.57(1.41,1.76)

1.39(1.22,1.59)

<0.0001

2.02(1.81,2.24)

1.68(1.48,1.90)

<0.0001

Hormone therapy (vs no)

 Yes

1.25(0.97,1.61)

—

 

1.25(1.13,1.38)

—

 
  1. Abbreviations: BMI, body mass index; CI, confidence interval; HR, hazards ratio. aHR: adjusted hazard ratio calculated by multiple variable Cox proportional hazards regression model for the risk of breast cancer after adjustment for all the variables include BMI, age, age at menarche, birth history, number of birth, age at the first full-term pregnancy, breast-feeding history and family history of breast cancer.
  2. aP-value for trend.
  3. bP-value=0.3575 for testing BMI ⩾35 vs BMI<35 (HR=0.82, 95% CI=0.54–1.25).
  4. cAmong parous women.
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