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Table 2 Relationship between duration of breastfeeding and risk of breast cancer among BRCA1 and BRCA2 mutation carriers.

From: Breastfeeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers

Breastfeeding duration N
(cases/controls)
Univariate
OR (95% CI)
P Multivariate1
OR (95% CI)
P
All subjects 1,665/1,665     
Never 389/327 1.00 (reference)   1.00 (reference)  
Ever 1,276/1,338 0.79 (0.67 to 0.94) 0.007 0.81 (0.68 to 0.97) 0.02
> 0 to ≤ 12 months 846/845 0.83 (0.69 to 0.99) 0.04 0.84 (0.70 to 1.02) 0.08
> 12 to ≤ 24 months 285/318 0.72 (0.58 to 0.90) 0.005 0.73 (0.58 to 0.93) 0.01
> 24 months 145/175 0.65 (0.49 to 0.86) 0.003 0.66 (0.49 to 0.89) 0.007
Per year   0.90 (0.84 to 0.97) 0.008 0.87 (0.79 to 0.95) 0.002
BRCA1 1,243/1,343     
Never 267/213 1.00 (reference)   1.00 (reference)  
Ever 976/1,030 0.74 (0.61 to 0.92) 0.005 0.76 (0.61 to 0.95) 0.02
> 0 to ≤ 12 months 669/658 0.79 (0.64 to 1.00) 0.03 0.81 (0.64 to 1.01) 0.06
> 12 to ≤ 24 months 212/236 0.68 (0.52 to 0.88) 0.004 0.68 (0.52 to 0.91) 0.008
> 24 months 94/136 0.50 (0.35 to 0.70) < 0.0001 0.51 (0.35 to 0.74) 0.0003
Per year   0.84 (0.77 to 0.93) 0.0003 0.81 (0.73 to 0.91) 0.002
BRCA2 422/422     
Never 122/114 1.00 (reference)   1.00 (reference)  
Ever 300/308 0.91 (0.67 to 1.23) 0.53 0.90 (0.64 to 1.25) 0.51
> 0 to ≤ 12 months 177/187 0.89 (0.64 to 1.23) 0.47 0.89 (0.63 to 1.25) 0.49
> 12 to ≤ 24 months 72/82 0.84 (0.54 to 1.28) 0.40 0.83 (0.53 to 1.31) 0.43
> 24 months 51/39 1.21 (0.72 to 2.03) 0.48 1.20 (0.68 to 2.11) 0.53
Per year   1.05 (0.91 to 1.21) 0.51 1.02 (0.85 to 1.21) 0.87
  1. 1Estimate adjusted for age at menarche (continuous), age at first birth (continuous), age at first birth (continuous), alcohol consumption (ever/never) and HRT use (ever/never).