Epidemiology of IBD | ||
| ULCERATIVE COLITIS | CROHN'S DISEASE | |
|---|---|---|
| Incidence (North America) per person-years | 0-19.2 per 100,000 | 0-20.2 per 100,000 |
| Age of onset | 15-30 and 60-80 | 15-30 and 60-80 |
| Ethnicity | Jewish > non-Jewish white > African American > Hispanic > Asian | |
| Male/female ratio | 0.51-1.58 | 0.34-1.65 |
| Smoking | May prevent disease (OR 0.58) | May cause disease (OR 1.76) |
| Oral contraceptives | No increased risk | OR 2.82 |
| Appendectomy | Protective (risk 13-26% lower) | Not protective |
| Monozygotic twins | 6-18% concordance | 38-58% concordance |
| Dizygotic twins | 0-2% concordance | 4% concordance |
| Antibiotic use in the first year of life | 2.9× the risk of developing childhood IBD | |
Abbreviations: IBD, inflammatory bowel disease; OR, odds ratio.