Table 2.

HRs and 95% CIs for the associations between physical activity and breast cancer risk, The Sister Study

OverallPremenopausalPostmenopausal
PYN casesHRa,b (95% CI)N casesHRa (95% CI)N casesHRa (95% CI)
Total average hours/week
 Continuous421,8073,0170.99 (0.97–1.00)5331.03 (1.00–1.06)2,4600.98 (0.96–0.99)
 0–<1140,4971,0351.001701.008591.00
 1–<4173,8721,2200.91 (0.84–0.99)2251.13 (0.92–1.38)9830.87 (0.79–0.95)
 4–<770,4255060.90 (0.81–1.01)951.29 (1.00–1.66)4080.83 (0.74–0.94)
 ≥737,0132560.85 (0.74–0.98)431.35 (0.96–1.89)2100.77 (0.66–0.90)
Total average MET-hours/week
 Continuous (IQR increase)421,8073,0170.97 (0.93–1.00)5331.08 (1.01–1.16)2,4600.92 (0.89–0.97)
 Quartile 1102,4817911.001211.006661.00
 Quartile 2110,5327530.86 (0.78–0.95)1310.99 (0.77–1.27)6160.83 (0.74–0.93)
 Quartile 3101,9717360.88 (0.79–0.97)1261.14 (0.88–1.47)6020.83 (0.74–0.92)
 Quartile 4106,8227370.83 (0.75–0.92)1551.25 (0.98–1.60)5760.75 (0.67–0.85)
At least one activity in the past 12 months
 No69,1055241.00731.004491.00
 Yes352,9432,4930.89 (0.81–0.98)4601.26 (0.98–1.62)2,0110.82 (0.74–0.91)
  • Abbreviations: PY, person-years.

  • aAdjusted for race, residence type, education, parity, alcohol use, and smoking status.

  • bBorderline violation of proportional hazards assumption.