Table 1.
Frequency of risk factors in breast cancer patients and controls and the adjusted odds ratios in relation to breast cancer riska
| Risk factor | Patients, % (n = 814) | Controls, % (n = 821) | aOR (95% CI) b |
|---|---|---|---|
| Age at menarche | |||
| >14 yr | 34.1 | 37.6 | 1.00 (reference) |
| ≤ 14 yr | 65.9 | 62.4 | 1.52 (1.18 to 1.96) |
| Menopause | |||
| No | 49.6 | 59.5 | 1.00 (reference) |
| Yes | 50.4 | 40.5 | 0.60 (0.42 to 0.84) |
| Family history of breast cancer in first-degree relatives | |||
| No | 88.7 | 90.7 | 1.00 (reference) |
| Yes | 11.3 | 9.3 | 1.20 (0.83 to 1.73) |
| Nulliparity | |||
| No | 11.6 | 10.2 | 1.00 (reference) |
| Yes | 88.4 | 89.8 | 0.67 (0.46 to 0.97) |
| No. of full-term pregnancies |
|||
| ≤ 2 | 51.0 | 45.6 | 1.00 (reference) |
| >2 | 49.0 | 54.4 | 0.46 (0.34 to 0.61) |
| Age at first full-term pregnancy |
|||
| ≤ 23 years | 62.6 | 64.0 | 1.00 (reference) |
| >23 years | 37.4 | 36.0 | 1.30 (1.00 to 1.69) |
| Body mass index | |||
| ≤ 23 | 56.9 | 59.1 | 1.00 (reference) |
| >23 | 43.1 | 40.9 | 0.90 (0.71 to 1.15) |
| Use of oral contraceptives | |||
| No | 81.4 | 82.1 | 1.00 (reference) |
| Ever | 18.6 | 17.9 | 1.05 (0.78 to 1.40) |
aaOR, adjusted odds ratio; 95% CI, 95% confidence interval; baOR and 95% CI were estimated in a logistic regression model in which the age of study participants was included.