Table 6.

Multivariable Cox regression model on the imputed datasets including all risk factors simultaneously, with 10-year breast cancer–specific mortality as endpoint.

Risk factorHR (95% CI)P
Age at menarche1.03 (1.00–1.05)1.4E-02
Parity
 0Ref.
 11.04 (0.90–1.21)5.5E-01
 21.00 (0.83–1.20)1.0E+00
 31.00 (0.81–1.24)1.0E+00
 4+1.01 (0.81–1.25)9.4E-01
Age at FFTP, y
 <20Ref.
 20–<250.90 (0.82–0.99)2.7E-02
 25–<300.87 (0.79–0.95)2.8E-03
 ≥300.80 (0.72–0.89)4.4E-05
Time since last full-term birth, y
 ≥10Ref.
 ≥5–< 101.16 (1.01–1.34)2.9E-02
 >0–< 51.36 (1.15–1.61)2.4E-04
Breastfeeding
 Ever vs. never0.98 (0.81–1.18)8.2E-01
 Duration of breastfeeding, per 6 mo1.02 (1.00–1.05)7.2E-02
BMI, kg/m2
 18.5–<25Ref.
 <18.51.10 (0.79–1.53)5.6E-01
 25–<301.06 (0.93–1.20)3.6E-01
 ≥301.16 (1.04–1.29)4.7E-03
Adult height, per 5 cm1.00 (0.95–1.06)8.7E-01
Oral contraceptive use
 Ever vs. never0.96 (0.89–1.03)2.5E-01
MHT
 Never use, postmenopausalRef.
 Formera use of ET0.82 (0.66–1.03)8.2E-02
 Formera use of EPT1.11 (0.91–1.35)3.2E-01
 Formera use (unknown type)0.88 (0.80–0.97)1.0E-02
 Currentb use of ET0.71 (0.57–0.89)2.6E-03
 Currentb use of EPT0.64 (0.54–0.76)2.3E-07
 Currentb use (unknown type)0.86 (0.76–0.97)1.3E-02
Smoking
 NeverRef.
 Formerc0.94 (0.88–1.01)7.2E-02
 Currentd1.11 (1.02–1.21)1.1E-02
Alcohol consumptiond, per 10 g/wk1.00 (0.99–1.01)8.4E-01
Cumulative alcohol consumption, per 10 g/d0.98 (0.91–1.06)5.2E-01
Physical activityd,e, hours/wk
 <1.8Ref.
 ≥1.8–<5.50.77 (0.22–2.73)6.4E-01
 ≥5.50.40 (0.13–1.19)5.7E-02
  • Note: The Cox model is stratified by and adjusted for lymph nodes status, tumor size, tumor grade, ER status, PR status, HER2 status, and (neo)adjuvant systemic treatment. Age of the patient was used as time scale. All risk factors were simultaneously included in the model. Corresponding complete-case analysis was based on 1,264 cases and 114 deaths from breast cancer. A comparison between results from imputed data analysis and corresponding complete-case analysis are shown in Supplementary Fig. S24.

  • Abbreviations: ET, estrogen therapy; EPT, combined estrogen and progestin therapy.

  • aMore than 6 mo before diagnosis.

  • bAt diagnosis or within 6 mo before diagnosis.

  • cMore than 1 year before diagnosis.

  • dAt diagnosis or within a year before diagnosis.

  • eCategories based on the tertiles of the observed distribution of the variable.