Table 1.
Population characteristics by body mass index (BMI) category at enrolment
| BMI category (kg/m2) | |||||
|---|---|---|---|---|---|
| Na | Underweight | Normal weight | Overweight | Obesity | |
| Number of women, n (%) | 135,708 | 3022 (2.2) | 87,595 (64.6) | 34,656 (25.5) | 10,435 (7.7) |
| Obesity-related cancer, n | 9328 | 173 | 5689 | 2603 | 863 |
| Characteristics at enrolment b | |||||
| Age (y), mean (SD) | 135,708 | 44.1 (8.4) | 46.9 (8.4) | 50.8 (8.4) | 51.5 (8) |
| Weight (kg), mean (SD) | 135,708 | 49.3 (3.9) | 61.4 (6.1) | 74.2 (6.3) | 91.0 (11.7) |
| Height (cm), mean (SD) | 135,708 | 166.6 (5.6) | 166.5 (5.6) | 165.9 (5.7) | 165.3 (5.8) |
| Education (y) % | 128,948 | ||||
| < 10 | 24.0 | 21.7 | 29.8 | 34.3 | |
| 10–12 | 22.1 | 23.5 | 24.6 | 24.4 | |
| > 12 | 53.9 | 54.9 | 45.6 | 41.3 | |
| Physical activity level % | 123,531 | ||||
| Low | 25.7 | 21.2 | 30.7 | 45.7 | |
| Moderate | 37.5 | 42.2 | 42.6 | 37.0 | |
| High | 36.8 | 36.7 | 26.7 | 17.4 | |
| Smoking status % | 135,231 | ||||
| Never smoker | 27.2 | 34.4 | 37.8 | 40.0 | |
| Former smoker | 21.3 | 31.8 | 35.7 | 36.2 | |
| Current smoker | 51.6 | 33.8 | 26.5 | 23.8 | |
| Alcohol intake (g/day), median | 128,046 | 1.6 | 1.9 | 1.5 | 0.9 |
| Age at menarche (y), mean (SD) | 133,625 | 13.7 (1.4) | 13.4 (1.4) | 13.2 (1.4) | 12.9 (1.4) |
| Age at first full-term pregnancy (y), mean (SD) | 123,592 | 24.7 (4.7) | 24.1 (4.4) | 23.6 (4.3) | 23.4 (4.4) |
| Parity % | 135,708 | ||||
| Nulliparous | 13.0 | 9.5 | 8.1 | 11.1 | |
| 1–2 children | 56.8 | 55.7 | 50.1 | 46.3 | |
| ≥ 3 children | 30.2 | 34.9 | 41.9 | 42.6 | |
| Oral contraceptive use % | 131,415 | ||||
| Never | 38.2 | 40.6 | 49.8 | 54.4 | |
| Ever | 61.8 | 59.4 | 50.2 | 45.6 | |
| Menopausal status % | 135,708 | ||||
| Premenopausal | 64.0 | 55.3 | 37.1 | 31.6 | |
| Perimenopausal | 4.2 | 4.8 | 5.6 | 6.6 | |
| Postmenopausal | 25.9 | 32.9 | 50.1 | 54.7 | |
| Unknown | 5.9 | 7.0 | 7.2 | 7.2 | |
| Age at menopause (y), mean (SD) | 45,160 | 46.7 (5.9) | 48.3 (4.8) | 48.8 (4.7) | 48.5 (5.2) |
| Hormone therapy use % | 126,669 | ||||
| Never | 85.7 | 79.6 | 72.7 | 73.7 | |
| Former | 5.6 | 8.2 | 12.9 | 14.4 | |
| Current | 8.7 | 12.2 | 14.4 | 11.9 | |
The Norwegian Women and Cancer study 1991–2005 (n = 135, 708)
a N is the total amount of responses for the specific variable
bOverall differences between weight change categories were significant for all variables (p < 0.001)
y years, SD standard deviation