Table 3.
Main effects exposure–response results for breast cancer incidence with a 10-year lag by subcohort: hazard ratio (95% CI).
| Variable | Full cohort (n = 5,752, cases = 281) | Questionnaire subcohorta (n = 3,952, cases = 201) | Restricted subcohortb (n = 3,141, cases = 145) |
|---|---|---|---|
| Model 1 | |||
| Cumulative exposure (per 1,000 unit-years) | 1.01 (0.96–1.05) | 1.00 (0.94–1.06) | 1.04 (0.97–1.11) |
| Born < 1920 (reference group) | 1.00 | 1.00 | 1.00 |
| Born 1920–1934 | 1.63 (1.19–2.23) | 1.71 (1.14–2.57) | 1.64 (0.96–2.83) |
| Born ≥ 1935 | 2.47 (1.65–3.70) | 2.86 (1.74–4.71) | 3.40 (1.79–6.46) |
| Model 2 | |||
| Years exposed | 1.01 (0.99–1.03) | 1.01 (0.99–1.03) | 1.02 (1.00–1.05) |
| Born < 1920 (reference group) | 1.00 | 1.00 | 1.00 |
| Born 1920–1934 | 1.62 (1.18–2.22) | 1.72 (1.14–2.58) | 1.66 (0.96–2.86) |
| Born ≥ 1935 | 2.50 (1.67–3.75) | 2.93 (1.78–4.84) | 3.52 (1.85–6.72) |
a
Questionnaire subcohort comprises members of the full cohort for whom some questionnaire data were available.
b
Restricted cohort comprises women with questionnaire data for ever smoking, parity, age at first live birth, breast cancer in first-degree female relative, hormone use, and age began hormone use.