Table 5.

HRs and 95% CIs for pre- to postdiagnosis change in lifestyle factors and the risk of a second breast cancer diagnosis: WISC DCIS cohort, 1997–2010

All second breast cancer diagnosesInvasive second breast cancer diagnoses
Second diagnosisHR (95% CI)bPtrendcSecond diagnosisHR (95% CI)bPtrendc
Change in BMIa,d
 Decrease > 0.13 kg/m2 per year330.95 (0.55–1.63)0.61131.06 (0.43–2.65)0.33
 Stable within ± 0.13 kg/m2 per year361.00 (Ref.)121.00 (Ref.)
 Increase > 0.13 kg/m2 per year710.88 (0.55–1.41)271.00 (0.44–2.26)
 Continuous for 1 kg/m2 per year change1400.98 (0.84–1.15)520.93 (0.71–1.21)
Change in total physical activitya,d
 Decrease > 0.13 h/wk per year190.95 (0.48–1.88)0.4561.00 (0.30–3.46)0.33
 Stable within ± 0.13 h/wk per year241.00 (Ref.)71.00 (Ref.)
 Increase > 0.13 h/wk per year110.74 (0.35–1.57)51.04 (0.30–3.67)
 Continuous for 1 h/wk change540.93 (0.73–1.20)181.02 (0.61–1.68)
Change in total alcohola,d
 Decrease > 0.064 drinks/wk per year70.73 (0.32–1.66)0.1330.62 (0.15–2.72)0.13
 Stable within ± 0.064 drinks/wk per year301.00 (Ref.)81.00 (Ref.)
 Increase > 0.064 drinks/wk per year171.58 (0.81–3.06)71.79 (0.61–5.47)
 Continuous for 1 drink/wk per year change541.01 (0.70–1.46)181.23 (0.67–2.16)
  • aCategories for BMI, physical activity, and alcohol intake represent the annualized change from prediagnosis to most recent postdiagnosis level (or last contact before a second breast diagnosis).

  • bAdjusted for age at diagnosis, menopausal status, mode of detection, treatment type, postmenopausal hormone use, tamoxifen use, year of diagnosis, tumor size, tumor grade, physical activity, alcohol use, time since diagnosis, remaining lifestyle factors, and prediagnosis levels of each lifestyle factor.

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

  • dCategories reflect a change of approximately 1 kg/m2 for BMI, 1 h/wk for physical activity, and 0.5 drinks/wk for alcohol intake over the median follow-up period.