Table 1. Breast cancer risk factors according to categories of MET-h per week among the 110 468 premenopausal women in the NHS II study population.
|
MET-h/Week−1 (median) |
|||||
|---|---|---|---|---|---|
| <3 (1.6) | 3–8.9 (5.8) | 9–17.9 (12.9) | 18–26.9 (21.9) | ⩾27 (41.7) | |
| Age (years) | 38.4 | 38.5 | 38.4 | 38.1 | 37.5 |
| BMI (kg m−2) | 26.3 | 25.7 | 25.1 | 24.7 | 24.1 |
| Height (cm) | 164 | 165 | 165 | 165 | 165 |
| Alcohol intake (g day−1) | 2.5 | 2.8 | 3.1 | 3.4 | 3.7 |
| Age at menarche <12 years (%) | 25 | 25 | 24 | 24 | 24 |
| Oral contraceptive user (%) | 9 | 10 | 10 | 11 | 11 |
| Nulliparous (%) | 19 | 19 | 21 | 24 | 28 |
| Parityb | 2.2 | 2.2 | 2.2 | 2.2 | 2.2 |
| Age at first birthb (years) | 26 | 26 | 26 | 26 | 26 |
| History of benign breast disease (%) | 34 | 36 | 36 | 35 | 35 |
| Mother or sister with breast cancer (%) | 6 | 7 | 6 | 6 | 6 |
a
Values are the mean or the percent of the person-time over follow-up from 1989 to 1999, standardized to the age distribution of the study population.
b
Parity and age at first birth were calculated among parous women only.