Table 3. Relative risks (RR) of breast cancer by time spent walking and by time spent running or jogging among premenopausal women in the NHS II cohort, 1989–1999.
| Person-years (thousands) | Cases | Age-adjusted RR (95% CI) | Multivariatea RR (95% CI) | |
|---|---|---|---|---|
| Walking | ||||
| <20 min week−1 | 166.2 | 126 | 1.00 | 1.00 |
| 20–59 min week−1 | 239.3 | 228 | 1.16 (0.93–1.44) | 1.17 (0.94–1.46) |
| 1–1.9 h week−1 | 251.9 | 241 | 1.20 (0.97–1.49) | 1.20 (0.97–1.50) |
| 2–3.9 h week−1 | 157.7 | 160 | 1.27 (1.00–1.60) | 1.23 (0.97–1.57) |
| ⩾4 h week−1 | 119.0 | 94 | 1.07 (0.82–1.40) | 1.07 (0.81–1.40) |
| P for linear trend | 0.74 | 0.80 | ||
| Running or jogging | ||||
| None | 760.4 | 701 | 1.00 | 1.00 |
| <1 h week−1 | 107.9 | 92 | 0.94 (0.76–1.17) | 0.92 (0.74–1.15) |
| 1–1.9 h week−1 | 36.5 | 37 | 1.20 (0.48–1.19) | 1.15 (0.83–1.61) |
| ⩾2 h week−1 | 29.3 | 19 | 0.76 (0.48–1.19) | 0.71 (0.45–1.12) |
| P for linear trend | 0.20 | 0.10 | ||
a
Adjusted for age, BMI, height, alcohol intake, age at menarche, age at first birth, oral contraceptive use, history of benign breast disease, mother or sister with breast cancer, and MET-h week−1 from other activities.