Table 4.

Evaluation of effect-measure modification by family history score for the associations between physical activity and breast cancer incidence, by menopausal status, The Sister Study

Family history scorePhysical activityN casesStratified HRa (95% CI)Ratio of stratified HRsP
Postmenopausal
 Low (<median)<7 hours/week9871.00
≥7 hours/week900.80 (0.64–0.99)
 High (≥median)<7 hours/week1,0431.00
≥7 hours/week980.91 (0.74–1.11)1.14 (0.84–1.53)0.4
 Low (<median)IQR increase in MET-hours/week1,0770.95 (0.88–1.01)
 High (≥median)IQR increase in MET-hours/week1,1410.92 (0.86–0.98)0.97 (0.88–1.07)0.6
Premenopausal
 Low (<median)<7 hours/week1081.00
≥7 hours/week70.78 (0.36–1.68)
 High (≥median)<7 hours/week3331.00
≥7 hours/week311.34 (0.93–1.94)1.72 (0.73–4.02)0.2
 Low (<median)IQR increase in MET-hours/week1151.02 (0.86–1.20)
 High (≥median)IQR increase in MET-hours/week3641.10 (1.02–1.19)1.08 (0.90–1.31)0.4
  • aAdjusted for race, residence type, education, parity, alcohol use, and smoking status.