A Cluster of Crohn's Disease in Ballybrack – Fact or Fiction?

Background: Clustering of Crohn's Disease (CD) although uncommon is recognised. The pathogenesis of CD is thought to involve an interaction between genetic and environmental factors; the latter may be important in clustering. Residents of Ballybrack raised the hypothesis that there was an increased prevalence of CD in that area.

Aim: To assess the prevalence of CD in Ballybrack vs. surrounding suburbs (Dun Laoghaire, Killiney, Sallynoggin, Cabinteely, Shankill) and if increased to identify possible aetiological factors.

Methods: A retrospective epidemiological study was performed to identify cases of CD in Ballybrack and surrounding suburbs referred to our hospital. Case finding was performed by reviewing a long established Inflammatory Bowel Disease database and HIPE data. Case notes were retrieved and diagnosis confirmed. Geographical boundaries were confirmed using district electoral maps. Prevalence rates were calculated using population estimates from the 2002 National Census. Possible associations with month of birth, gender, family history, smoking or surgery were analysed using multivariate logistic regression.

Results: There was an association between CD and Ballybrack (P=0.014), however no association was found with month of birth, gender, family history, smoking or surgery. The prevalence of CD in Ballybrack was calculated as 6.7/1000 population compared with 1.7/1000 population in surrounding suburbs.

Conclusion: This study demonstrates an increased prevalence of CD in Ballybrack, however no conclusions can be made in terms of aetiology can be made. Further possible aetiological factors are being investigated at this time.