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. 2012 Dec;61(12):1686-92.
doi: 10.1136/gutjnl-2011-301574. Epub 2012 Jan 11.

Geographical variation and incidence of inflammatory bowel disease among US women

Hamed Khalili  1 , Edward S Huang, Ashwin N Ananthakrishnan, Leslie Higuchi, James M Richter, Charles S Fuchs, Andrew T Chan
Affiliations

Geographical variation and incidence of inflammatory bowel disease among US women

Hamed Khalili et al. Gut. 2012 Dec.

Abstract

Objective: Geographical variation in the incidence of Crohn's disease (CD) and ulcerative colitis (UC) according to the latitude of residence has been reported in Europe. However, there are no comparable data in the USA. The incidence of CD and UC in relation to latitude was assessed in a geographically diverse population of women enrolled in two large prospective studies in the USA.

Design: A prospective study was undertaken of women enrolled in the Nurses' Health Study I (NHS) in 1976 and in the NHS II in 1989. Information on state of residence at the time of birth, at age 15 years and age 30 years was collected in 1992 in NHS I and in 1993 in NHS II. Reported diagnoses of incident CD or UC to the end of 2003 were confirmed by medical record review. Cox proportional hazards models were used to calculate HRs and 95% CIs for risk of CD and UC.

Results: In both cohorts, among 175,912 women reporting their residence in 1992, 257 cases of CD and 313 cases of UC were documented over 3,428,376 person-years of follow-up. The incidence of CD and UC increased significantly with increasing latitude (p(trend)<0.01), with residence at age 30 years more strongly associated with risk. Compared with women residing in northern latitudes at age 30, the multivariate-adjusted HR for women residing in southern latitudes was 0.48 (95% CI 0.30 to 0.77) for CD and 0.62 (95% CI 0.42 to 0.90) for UC. The effect of latitude of residence on risk of CD and UC did not vary according to smoking history (p(interaction)=0.26 for CD and 0.99 for UC).

Conclusion: In a population of US women, increasing latitude of residence was associated with a higher incidence of CD and UC.

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Conflict of interest statement

Competing interests ATC has previously served as a consultant for Bayer Healthcare and Millennium Pharmaceuticals.

Figures

Figure 1
Figure 1
Comparison of age-specific incidence rates of Crohn’s disease in the Nurses’ Health Study (NHS), Kaiser Permanente and Olmsted County cohorts.
Figure 2
Figure 2
Comparison of age-specific incidence rates of ulcerative colitis in the Nurses’ Health Study (NHS), Kaiser Permanente and Olmsted County cohorts.
See this image and copyright information in PMC

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