title: Geographical variation of Crohn's disease residual incidence in the Province of Quebec, Canada.
abstract: BACKGROUND
  Crohn's disease (CD) is clinically expressed as a chronic affection of the gastrointestinal tract currently known to have a multifactorial etiology involving a complex pathophysiological host response modulated by genetic susceptibilities, demographic determinants and environmental factors. With more than 20 cases per 100,000 person-years, the province of Quebec, Canada is among regions of the world with highest reported occurrence of CD in relation to other places where comparable estimates are available. This ecological study was designed to provide a medium-scale spatial exploration of CD incidence after accounting for the influence of known population and regional determinants. Health records of consulting patients in southern Quebec were compiled from 1995 to 2000 and used to estimate age and sex standardized rates per health area (n = 156). Various statistical models taking into account the regional effect of Jewish ethnicity, aboriginal ancestry, material deprivation, prescription for oral contraceptives, reportable enteric infection incidence, smoking as well as latitude and longitude locations were fitted.
  
  
  RESULTS
  The final regression model presented a coefficient of determination of 22.8% and there was evidence of an eastern trend in the residual incidence (p = 0.018). Overall, the smoothed residual incidence presented a heterogeneous spatial pattern with evidence of patches (multiple health areas) of high, low and contrasting values. Health areas with most extreme incidence residuals where also distributed over the whole province including one area in the metropolitan area of Montreal and others in surrounding areas.
  
  
  CONCLUSIONS
  These findings suggest that known populational and regional factors derived through census information only explain a limited fraction of the geographical variation of CD incidence and lead to speculate that the effects of these factors may be incompletely captured (imperfect construction of proxy variables) or that other important factors remain unmeasured. In this view, markers of genetic profiles of homogeneous sub-populations, and other factors linked to agroenvironmental microbial exposure should be further investigated. Once accounting for known factors, it would also be worth comparing adjacent geographical areas demonstrating abrupt changes in residual incidence rates to further explore effect linked to regional factors from those resulting from various reporting systems.
authors.affiliation: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Saint-Hyacinthe, Quebec, Canada. pascal_michel@phac-aspc.gc.ca
authors.forename: Pascal
authors.initials: P
authors.lastname: Michel
authors.forename: Laurie
authors.initials: L
authors.lastname: St-Onge
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Lowe
authors.forename: Michel
authors.initials: M
authors.lastname: Bigras-Poulin
authors.forename: Paul
authors.initials: P
authors.lastname: Brassard
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D003424:Crohn Disease / Q000453:epidemiology* / Q000208:ethnology / Q000235:genetics; D003710:Demography; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data*; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology*; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016012:Poisson Distribution; D011237:Predictive Value of Tests; D011336:Probability; D011792:Quebec / Q000453:epidemiology; D012044:Regression Analysis; D012189:Retrospective Studies; D018570:Risk Assessment; D017678:Sex Distribution; D055815:Young Adult
references.citation: Curr Opin Gastroenterol. 2008 Jan;24(1):17-21
references.pmid: 18043227
references.citation: Best Pract Res Clin Gastroenterol. 2009;23(2):233-43
references.pmid: 19414149
references.citation: Aliment Pharmacol Ther. 2002 Nov;16(11):1903-15
references.pmid: 12390099
references.citation: Med Sci (Paris). 2007 Nov;23(11):997-1001
references.pmid: 18021714
references.citation: J Gastroenterol Hepatol. 2008 Dec;23(12):1794-801
references.pmid: 19120872
references.citation: Orv Hetil. 2005 Apr 24;146(17):797-802
references.pmid: 17918636
references.citation: Scand J Gastroenterol. 2008 Aug;43(8):961-6
references.pmid: 19086166
references.citation: Am J Epidemiol. 1999 May 15;149(10):916-24
references.pmid: 10342800
references.citation: Am J Gastroenterol. 2001 Apr;96(4):1101-5
references.pmid: 11316154
references.citation: Inflamm Bowel Dis. 2006 Jan;12 Suppl 1:S3-9
references.pmid: 16378007
references.citation: Am J Phys Anthropol. 2009 Aug;139(4):512-22
references.pmid: 19226649
references.citation: Am J Epidemiol. 2001 Aug 15;154(4):328-35
references.pmid: 11495856
references.citation: Environ Health Perspect. 2008 Aug;116(8):1098-104
references.pmid: 18709174
references.citation: Clin Genet. 2005 Oct;68(4):287-301
references.pmid: 16143014
references.citation: Am J Epidemiol. 2008 Nov 1;168(9):1065-72
references.pmid: 18801890
references.citation: Med Hypotheses. 2009 Jul;73(1):94-6
references.pmid: 19269107
references.citation: Inflamm Bowel Dis. 2010 May;16(5):807-12
references.pmid: 19774647
references.citation: Eur Heart J. 1999 Dec;20(23):1689-91
references.pmid: 10562474
references.citation: Ann Agric Environ Med. 2008;15(2):193-7
references.pmid: 19061254
references.citation: Curr Pharm Des. 2009;15(18):2074-86
references.pmid: 19519445
references.citation: Inflamm Bowel Dis. 2009 Mar;15(3):429-35
references.pmid: 18942744
references.citation: Am J Gastroenterol. 2009 Sep;104(9):2233-40
references.pmid: 19513023
references.citation: Annu Rev Genomics Hum Genet. 2001;2:69-101
references.pmid: 11701644
references.citation: Curr Opin Gastroenterol. 2009 Jul;25(4):301-5
references.pmid: 19349861
references.citation: J Dig Dis. 2009 Feb;10(1):1-6
references.pmid: 19236540
references.citation: Inflamm Bowel Dis. 2006 Mar;12(3):212-7
references.pmid: 16534423
references.citation: Am J Gastroenterol. 2006 Jul;101(7):1559-68
references.pmid: 16863561
references.citation: Indian J Med Res. 2009 Aug;130(2):133-7
references.pmid: 19797809
references.citation: J Clin Epidemiol. 2005 Feb;58(2):206-8
references.pmid: 15680756
references.citation: Scand J Gastroenterol. 2006 Apr;41(4):437-44
references.pmid: 16635912
references.citation: World J Gastroenterol. 2009 Jun 7;15(21):2570-8
references.pmid: 19496185
references.citation: Am J Epidemiol. 2006 Oct 1;164(7):615-23; discussion 624-8
references.pmid: 16920784
references.citation: Pharmacoepidemiol Drug Saf. 2006 Jan;15(1):19-29
references.pmid: 16136613
references.citation: World J Gastroenterol. 2010 Jan 28;16(4):431-8
references.pmid: 20101767
references.citation: Inflamm Bowel Dis. 2009 Apr;15(4):608-15
references.pmid: 19067408
references.citation: World J Gastroenterol. 2009 May 7;15(17):2081-8
references.pmid: 19418580
references.citation: Curr Opin Gastroenterol. 2008 Jul;24(4):440-7
references.pmid: 18622157
references.citation: Inflamm Bowel Dis. 2006 Mar;12(3):218-26
references.pmid: 16534424
references.citation: Inflamm Bowel Dis. 2008 Jul;14(7):984-91
references.pmid: 18338775