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Table 3 Risk of invasive or in situ breast cancer in relation to duration between pubertal events

From: Timing of pubertal stages and breast cancer risk: the Breakthrough Generations Study

  Adjusted for attained age   Multivariate-adjusteda  
Pubertal variable Ncases/person-years HR (95% CI)   Ncases/person-years HR (95% CI)
Thelarche to menarche, years
<0 57/27,759 0.85 (0.64,1.13)   57/27,381 0.87 (0.65,1.15)  
0 275/112,810 Referent   271/111,168 Referent  
1 303/116,433 1.14 (0.97,1.34)   299/114,967 1.14 (0.96,1.34)  
≥2 156/61,061 1.27 (1.05,1.55) * 155/60,301 1.27 (1.04,1.55) *
P for trend   1.14 (1.05, 1.23) **   1.13 (1.05, 1.23) **
Thelarche to regular periods, years
<0 24/9,864 0.88 (0.57,1.36)   24/9,734 0.89 (0.58,1.38)  
0 129/46,383 Referent   127/45,750 Referent  
1 179/71,457 0.93 (0.74,1.16)   177/70,595 0.92 (0.73,1.15)  
≥2 188/81,162 0.94 (0.75,1.18)   187/80,149 0.93 (0.74,1.16)  
Never became 73/26,114 1.19 (0.89,1.59)   73/25,581 1.19 (0.89,1.58)  
regular
P for trendb   0.99 (0.90, 1.09)    0.98 (0.89, 1.08)  
Menarche to regular periods, years
0 379/134,744 Referent   376/132,702 Referent  
1 180/71,866 0.88 (0.74,1.06)   178/70,749 0.87 (0.73,1.04)  
≥2 54/31,244 0.67 (0.51,0.90) ** 54/30,778 0.66 (0.50,0.88) **
Never became 73/26,114 1.14 (0.89,1.47)   73/25,581 1.13 (0.88,1.46)  
regular
P for trendb   0.84 (0.75, 0.95) **   0.84 (0.74, 0.94) **
Menarche to adult height, years
<0 14/5,941 0.90 (0.52,1.56)   14/5,871 0.90 (0.52,1.57)  
0 to 1 131/50,937 Referent   130/50,492 Referent  
2-3 191/83,968 0.98 (0.79,1.23)   189/82,911 0.96 (0.77,1.21)  
≥4 165/78,925 0.94 (0.75,1.19)   165/77,560 0.94 (0.75,1.19)  
P for trend   0.98 (0.89, 1.09)    0.98 (0.88, 1.09)  
  1. CI, Confidence interval; HR, Hazard ratio.
  2. *P <0.05; **P <0.01; *** P<0.001.
  3. aAdjusted for attained age, menopausal status, family history of breast cancer in a first-degree relative, adult height, age at first full-term pregnancy (with a term for nulliparous women) and HRT status.
  4. bTest for trend excludes those who had never had a regular period.