Table 1.
Demographic characteristics of inflammatory bowel disease (IBD) cases and controls by country of recruitment
| Crohn’s disease |
Ulcerative colitis |
Control |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| China n = 113 | India n = 25 | USA n = 192 | China n = 51 | India n = 65 | USA n = 151 | China n = 173 | India n = 104 | USA n = 302 | |
| Female | 38.1% | 24.0% | 62.5% | 60.8% | 44.6% | 67.6% | 49.1% | 23.1% | 71.5% |
| Age at questionnaire | 27.5 | 29.8 | 37.1 | 34.3 | 33.5 | 42.5 | 29.1 | 45.7 | 36.8 |
| Year, median, min–max | 18–50 | 18–65 | 18–82 | 19–60 | 18–65 | 20–76 | 18–67 | 20–74 | 18–76 |
| Duration of IBD at questionnaire | 1.9 | 1.5 | 11.0 | 2.0 | 1.9 | 8.7 | N/A | N/A | N/A |
| Year, median, min-max | 0–12.7 | 0–14.2 | 0–49.0 | 0–12.0 | 0–17.6 | 0–46.3 | |||
| Age at IBD diagnosis | 26.0 | 28.4 | 25.0 | 32.0 | 28.5 | 29.2 | N/A | N/A | N/A |
| Year, median, min–max | 13–77 | 17–51 | 5–73 | 16–56 | 15–64 | 10–70 | |||
| ≤12 | 0 | 0 | 5.2% | 0 | 0 | 3.3% | |||
| 13–17 | 9.7% | 4.0% | 15.6% | 2.0% | 4.6% | 5.3% | |||
| 18–25 | 40.7% | 24.0% | 33.3% | 29.4% | 36.9% | 31.1% | |||
| 26–39 | 40.7% | 64.0% | 28.7% | 37.2% | 33.9% | 37.8% | |||
| ≥40 | 8.9% | 8.0% | 17.2% | 31.4% | 24.6% | 22.5% | |||
| Calendar year of IBD diagnosis | 2015 | 2015 | 2005 | 2014 | 2014 | 2006 | N/A | N/A | N/A |
| Median, min–max | 2003–2016 | 2002–2017 | 1966–2016 | 2003–2017 | 1997–2017 | 1969–2016 | |||
| ≤1970 | 0 | 0 | 1.0% | 0 | 0 | 0.7% | |||
| 1971–1980 | 0 | 0 | 7.3% | 0 | 0 | 4.0% | |||
| 1981–1990 | 0 | 0 | 10.4% | 0 | 0 | 10.6% | |||
| 1991–2000 | 0 | 0 | 18.8% | 0 | 3.1% | 14.6% | |||
| 2001–2010 | 13.3% | 12.0% | 36.5% | 7.8% | 18.5% | 37.1% | |||
| ≥2011 | 86.7% | 88.0% | 26.0% | 92.2% | 78.4% | 33.1% | |||
| Any family history of IBD | 7.1% | 12.0% | 40.1% | 3.9% | 7.7% | 40.4% | N/Aa | N/A | N/A |
| Proportion matched (N matched/ total)b | 107/113 | 25/25 | 55/219 | 46/51 | 62/65 | 39/151 | 154/173 | 97/104 | 125/302 |
| Relationship to case | N/A | N/A | N/A | N/A | N/A | N/A | |||
| Parent | 1.2% | 30.8% | 4.0% | ||||||
| Offspring | 2.3% | 5.8% | 4.3% | ||||||
| Sibling | 76.3% | 17.3% | 15.6% | ||||||
| Partner/spouse | 4.6% | 29.8% | 14.2% | ||||||
| Other relative | 1.7% | 6.7% | 0.7% | ||||||
| Friend | 2.9% | 2.9% | 2.6% | ||||||
| Independently recruited | 11.0% | 6.7% | 58.6% | ||||||
a
The prevalence of IBD family history for controls is not listed, as it would not reflect the prevalence of family history among individuals without inflammatory bowel disease in the source or target population, due to the recruiting mechanism of the present study where cases refer their family or friend without IBD to serve as controls
b
All participants contributed to the main analysis. The subset of matched case-control pairs contributed to the match case–control analysis