Table 1.
Age-standardized distribution of selected personal characteristics of person-years of follow-up according to active and passive smoking status.
| Personal Characteristics | Active Smoking | Passive Smoking | ||||
|---|---|---|---|---|---|---|
| Never | Past | Current | Never | Occasionally | Regularly | |
| Age (years) (mean) | 56.3 | 58.2 | 52.4 | 59.6 | 59.4 | 59.1 |
| Family History (%) | 15.0 | 15.9 | 14.5 | 15.7 | 15.7 | 15.6 |
| History of benign breast disease (%) | 48.2 | 51.4 | 44.2 | 49.1 | 50.2 | 49.6 |
| Nulliparous (%) | 6.8 | 6.6 | 7.3 | 6.4 | 6.3 | 7.2 |
| Parous: | ||||||
| Number of children (mean) | 3.2 | 3.1 | 3.2 | 3.1 | 3.2 | 3.2 |
| Age at first birth (years) (mean) | 24.9 | 24.8 | 24.7 | 25.2 | 24.8 | 24.6 |
| Body mass index (mean) (kg/m2) | 25.8 | 25.9 | 24.4 | 25.5 | 26.0 | 26.8 |
| Body mass index at 18 (mean) (kg/m2) | 21.1 | 21.4 | 21.6 | 21.0 | 21.1 | 21.2 |
| Postmenopausal (%) | 63.6 | 64.5 | 68.3 | 75.0 | 74.7 | 75.1 |
| Used OC (%) | 46.2 | 51.9 | 46.6 | 46.1 | 46.9 | 48.5 |
| Alcohol consumption (grams/day) (mean) | 3.6 | 6.8 | 8.6 | 3.3 | 3.7 | 3.4 |
*
At baseline of 1976, a total of 111,140 participants of NHS were included in the analysis of active smoking. At baseline of 1982, a total of 36,017 participants of NHS were included in the analysis of passive smoking.