Table 5.
Oral contraceptive use and risk of Crohn's disease according to strata of age, smoking and body mass index
| Never | Ever | Pinteraction | |
|---|---|---|---|
| Age ≤40 years | 0.09 | ||
| No of cases/person-years | 34/610188 | 154/2 079 577 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.18 (0.81 to 1.73) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.09 (0.74 to 1.61) | |
| Age >40 years | |||
| No of cases/person-years | 62/1 449 807 | 65/890624 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.89 (1.29 to 2.75) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.73 (1.18 to 2.53) | |
| Never smoking | 0.72 | ||
| No of cases/person-years | 42/1 012 745 | 100/1 571 377 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.20 (0.79 to 1.83) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.17 (0.76 to 1.78) | |
| Past/current smoking | |||
| No of cases/person-years | 54/1 047 250 | 1 19/1 398 823 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.76 (1.22 to 2.55) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.65 (1.14 to 2.40) | |
| Body mass index <25 kg/m2 | 0.08 | ||
| No of cases/person-years | 71/1 385 147 | 154/2 180 254 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.39 (1.00 to 1.92) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.26 (0.91 to 1.75) | |
| Body mass index ≥25 kg/m2 | |||
| No of cases/person-years | 25/674 848 | 65/789 947 | |
| Age-adjusted HR, 95% CI | 1.00 | 1.91 (1.11 to 3.31) | |
| Multivariate-adjusted HR, 95% CI* | 1.00 | 1.89 (1.08 to 3.28) | |
*
Models adjusted for age (months), cohort (NHS I, NHS II), smoking (never, past, current), body mass index (<20, 20—24.9, 25—29.9, ≥30 kg/m2), oral contraceptive use (never, past, current), parity (nulliparous, parous), age at menarche (≤10, 11, 12, 13, ≥14 years), hormonal replacement therapy (never, past, current) and menopause status (pre-menopause, natural menopause, surgical/radiation menopause), cohort (NHS I, NHS II) and questionnaire cycle. Models were adjusted for these covariates minus the strata variable (age, smoking and body mass index).