Table 2.

HRs and 95% CIs for the association between BMI and the risk of a second breast cancer diagnosis: WISC DCIS cohort, 1997–2010

All second breast cancer diagnosesInvasive second breast cancer diagnoses
Prediagnosis (N = 1,925)Postdiagnosis (N = 1,903)bPrediagnosis (N = 1,925)Postdiagnosis (N = 1,903)b
Second diagnosisHR (95% CI)aPtrendcHR (95% CI)aPtrendcSecond diagnosisHR (95% CI)aPtrendcHR (95% CI)aPtrendc
All women (kg/m2)
 <25.0781.00 (Ref)0.271.00 (Ref.)0.21261.00 (Ref.)0.751.00 (Ref.)0.64
 25–29.9561.10 (0.77–1.58)1.03 (0.60–1.44)221.29 (0.71–2.35)0.71 (0.32–1.55)
 30+280.83 (0.53–1.30)1.15 (0.52–2.13)90.82 (0.38–1.81)1.34 (0.44–4.07)
 Continuous per 1 kg/m21620.99 (0.96–1.02)1.03 (0.97–1.10)570.99 (0.94–1.04)1.00 (0.90–1.11)
Premenopausal women (kg/m2)
 <25.0501.00 (Ref.)0.191.00 (Ref.)0.44181.00 (Ref.)0.041.00 (Ref.)0.43
 25–29.9200.83 (0.48–1.43)1.17 (0.54–2.11)50.53 (0.18–1.49)0.40 (0.11–1.45)
 30+40.23 (0.07–0.71)1.14 (0.33–3.92)10.16 (0.02–1.28)0.50 (0.05–5.42)
 Continuous per 1 kg/m2740.93 (0.88–0.99)1.04 (0.95–1.13)240.87 (0.74–0.99)0.95 (0.82–1.13)
Postmenopausal women (kg/m2)
 <25.0281.00 (Ref.)0.371.00 (Ref.)0.2281.00 (Ref.)0.891.00 (Ref.)0.22
 25–29.9361.53 (0.91–2.57)1.04 (0.50–1.79)171.93 (0.75–4.13)1.26 (0.41–3.88)
 30+241.50 (0.84–2.66)1.21 (0.42–2.45)81.17 (0.63–4.95)2.39 (0.57–10.1)
 Continuous per 1 kg/m2881.03 (0.99–1.06)1.03 (0.94–1.12)331.03 (0.97–1.10)1.03 (0.90–1.18)
  • aAdjusted for age at diagnosis, menopausal status, mode of detection, treatment type, postmenopausal hormone use, tamoxifen use, year of diagnosis, tumor size, tumor grade, and remaining lifestyle factors.

  • bPostdiagnosis results are additionally adjusted for prediagnosis levels of each lifestyle factor.

  • cP is for linear trend across categories of each lifestyle factor.