The Relationship Between Urban Environment and Inflammatory Bowel Disease: A Systematic Review and Meta-analysis
Bibliographic record
Abstract
Purpose: Residing in an urban environment has been associated with the inflammatory bowel diseases (IBD). The objectives of our study were to conduct a systematic review with meta-analysis of studies assessing the association between urban environment and both ulcerative colitis (UC) and Crohn's disease (CD). Methods: A systematic literature search of MEDLINE (1950 to Oct. 2009) and EMBASE (1980 to Oct. 2009) databases was conducted to identify studies investigating the relationship between urban environment and IBD. The search was not limited by language to ensure capture of all appropriate papers. Two reviewers identified eligible articles based on the following pre-determined criteria: (1) investigated environmental risk factors for IBD in a case-control design or investigated the epidemiology of IBD using incident cases; (2) reported or provided enough information to calculate a measure of association between urban environment and IBD; and (3) UC and/or CD were reported separately. Studies not based on original data were excluded. Cohort and case-control studies were analyzed using incidence rate ratio (IRR) and odds ratio (OR) with 95% CIs, respectively. Random effects analyses were used given the potential heterogeneity between studies. Stratified and sensitivity analyses were performed to explore factors that may explain heterogeneity between studies (e.g. publication year, geographic region, timing of exposure) and to assess the effects of selected study quality. Results: The search strategy retrieved 6940 unique citations and 30 studies were selected for inclusion. Of these, 20 investigated the relationship between urban environment and UC and 22 investigated this relationship with CD. Therefore, included in our analysis were 5 case-control UC studies, 7 case-control CD studies, 15 cohort UC studies and 15 cohort CD studies. Based on a random effects model, the pooled IRRs for UC and CD cohort studies were 1.20 (1.02, 1.41) and 1.37 (1.20, 1.58), respectively. For case-control studies the pooled ORs for UC and CD were 1.28 (0.99, 1.65) and 1.35 (1.23, 1.62), respectively. These associations persisted across multiple stratified and sensitivity analyses exploring clinical and study quality factors. Heterogeneity was observed in the cohort studies for both UC and CD, whereas statistically significant heterogeneity was not observed for the case-control studies. Conclusion: A positive association between urban environment and both CD and UC was found. Heterogeneity may be explained by differences in study design and quality factors.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.018 | 0.046 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.020 | 0.026 |
| Bibliometrics | 0.012 | 0.015 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".