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Geographical variation of Crohn's disease residual incidence in the Province of Quebec, Canada.

Michel P, St-Onge L, Lowe AM, Bigras-Poulin M, Brassard P - Int J Health Geogr (2010)

Bottom Line: 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.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Saint-Hyacinthe, Quebec, Canada. pascal_michel@phac-aspc.gc.ca

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.

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Crohn's Disease Standardized Cumulative Incidence (1995 - 2000). Incidence rates were transformed using empirical Bayesian smoothing function (EBS) and represent age and sex directly standardized cumulative measures. The classification is based on a standard deviation bi-directional method.
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Figure 1: Crohn's Disease Standardized Cumulative Incidence (1995 - 2000). Incidence rates were transformed using empirical Bayesian smoothing function (EBS) and represent age and sex directly standardized cumulative measures. The classification is based on a standard deviation bi-directional method.

Mentions: The spatial distribution of the EBS CD standardized cumulative incidence in southern Quebec followed an overall heterogeneous pattern. Some regions included health areas with very high rates, other regions showed homogeneous patches of health areas with low and very low rates and several locations showed a combination of high and low incidence, the highest incidence areas being adjacent to lower incidence areas (Figure 1). After accounting for the effect of selected factors in the main model (Table 1), the spatial distribution of regional EBS cumulative incidence residuals was also heterogeneous, presenting a similar but more contrasted pattern when compared to the distribution of the incidence rates. In Figure 2, positive values reflect a larger observed incidence than the one predicted by the model (under-estimation by the model) and negative values reflect a smaller observed incidence than the one predicted by the model (over-estimation by the model). Patches of health areas with lower values such as regions identified as A and E, higher values (i.e. regions B and F) and with discordant values (i.e. regions D and C) were spread over the province with no specific geographical pattern. For the Island of Montreal (Figure 2, inset), the areas corresponding to the greater downtown sectors had, for the most part, large or very large negative residuals and the rest of the island presented overall large positive residuals. For Quebec city (not shown), the second largest metropolitan area after Montreal in this province, the upper town area (including the business downtown and tourist center) presented large negative residuals and the lower town area, the sub-urban northern and southern areas of the city showed large and very large positive residuals.


Geographical variation of Crohn's disease residual incidence in the Province of Quebec, Canada.

Michel P, St-Onge L, Lowe AM, Bigras-Poulin M, Brassard P - Int J Health Geogr (2010)

Crohn's Disease Standardized Cumulative Incidence (1995 - 2000). Incidence rates were transformed using empirical Bayesian smoothing function (EBS) and represent age and sex directly standardized cumulative measures. The classification is based on a standard deviation bi-directional method.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2877008&req=5

Figure 1: Crohn's Disease Standardized Cumulative Incidence (1995 - 2000). Incidence rates were transformed using empirical Bayesian smoothing function (EBS) and represent age and sex directly standardized cumulative measures. The classification is based on a standard deviation bi-directional method.
Mentions: The spatial distribution of the EBS CD standardized cumulative incidence in southern Quebec followed an overall heterogeneous pattern. Some regions included health areas with very high rates, other regions showed homogeneous patches of health areas with low and very low rates and several locations showed a combination of high and low incidence, the highest incidence areas being adjacent to lower incidence areas (Figure 1). After accounting for the effect of selected factors in the main model (Table 1), the spatial distribution of regional EBS cumulative incidence residuals was also heterogeneous, presenting a similar but more contrasted pattern when compared to the distribution of the incidence rates. In Figure 2, positive values reflect a larger observed incidence than the one predicted by the model (under-estimation by the model) and negative values reflect a smaller observed incidence than the one predicted by the model (over-estimation by the model). Patches of health areas with lower values such as regions identified as A and E, higher values (i.e. regions B and F) and with discordant values (i.e. regions D and C) were spread over the province with no specific geographical pattern. For the Island of Montreal (Figure 2, inset), the areas corresponding to the greater downtown sectors had, for the most part, large or very large negative residuals and the rest of the island presented overall large positive residuals. For Quebec city (not shown), the second largest metropolitan area after Montreal in this province, the upper town area (including the business downtown and tourist center) presented large negative residuals and the lower town area, the sub-urban northern and southern areas of the city showed large and very large positive residuals.

Bottom Line: 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.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Saint-Hyacinthe, Quebec, Canada. pascal_michel@phac-aspc.gc.ca

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.

Show MeSH
Related in: MedlinePlus