Table 2.
Association between physical activity and risk of invasive breast cancer by menopausal status in UK Biobank (n = 174,160 women followed from 2006 to 2014).
| Self-reported physical activity quartiles | Median self-reported physical activity | Repeat median self-reported physical activity | Median accelerometer physical activity | Cases/total (n) | Relative risk | Relative risk |
|---|---|---|---|---|---|---|
| (MET hrs/week) | (MET hrs/week) | (MET hrs/week) | (milli-gravity/week) | (95% g-s CI)a | (95% g-s CI)b | |
| Premenopausal women | ||||||
| 0–13.78 | 7.30 | 15.40 | 27.34 | 205/12,324 | 1.00 (0.87–1.15) | 1.00 (0.87–1.15) |
| 13.79–29.55 | 21.12 | 23.10 | 29.47 | 200/12,318 | 0.97 (0.84–1.11) | 0.95 (0.83–1.09) |
| 29.56–58.27 | 40.80 | 34.22 | 31.25 | 183/12,261 | 0.91 (0.79–1.05) | 0.89 (0.77–1.03) |
| ≥58.28 | 91.80 | 64.40 | 33.24 | 129/10,553 | 0.77 (0.65–0.92) | 0.75 (0.63–0.89) |
| Linear trend per 50 MET hours/week (corrected with repeat self-reported physical activity) | 0.77 (0.62–0.95) | 0.74 (0.60–0.92) | ||||
| P for trend | 0.015 | 0.008 | ||||
| Linear trend per 5 milli-gravity (using median accelerometer values) | 0.82 (0.69-0.97) | 0.79 (0.66-0.95) | ||||
| P for trend | 0.022 | 0.010 | ||||
| Postmenopausal women | ||||||
| 0–13.78 | 7.53 | 13.20 | 25.12 | 614/31271 | 1.00 (0.92–1.08) | 1.00 (0.92–1.08) |
| 13.79–29.55 | 21.17 | 23.89 | 26.83 | 611/31,196 | 0.99 (0.91–1.07) | 1.01 (0.94–1.10) |
| 29.56–58.27 | 41.10 | 38.75 | 27.77 | 553/31255 | 0.88 (0.81–0.96) | 0.92 (0.84–1.00) |
| ≥58.28 | 95.10 | 63.10 | 29.39 | 537/32,982 | 0.83 (0.76–0.90) | 0.87 (0.80–0.95) |
| Linear trend per 50 MET hours/week (corrected with repeat self-reported physical activity) | 0.81 (0.73–0.91) | 0.85 (0.76–0.96) | ||||
| P for trend | 0.000 | 0.006 | ||||
| Linear trend per 5 milli-gravity (using median accelerometer values) | 0.79 (0.69–0.90) | 0.84 (0.73–0.96) | ||||
| P for trend | <0.001 | 0.010 | ||||
| P for heterogeneity by menopausal status (corrected with repeat self-reported physical activity) = 0.26 | ||||||
| P for heterogeneity by menopausal status (using median accelerometer values) = 0.61 | ||||||
MET hrs/week metabolic equivalent hours per week; g-s CI group-specific confidence interval
aStratified by age at recruitment, region of recruitment and socioeconomic status. Adjusted for family history of breast cancer, height, parity, age at menarche, oral contraceptive use, age at first birth, smoking status, ever had breast cancer screening, alcohol intake frequency, age at menopause and HRT use (only in postmenopausal women)
bFurther adjusted for quartiles of body fat mass within each menopausal status group