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It is unclear whether obesity is associated with the development of inflammatory bowel disease despite compelling data from basic science studies. We therefore examined the association between obesity and risk of Crohn's disease (CD) and ulcerative colitis (UC). METHODS:We conducted pooled analyses of 5 prospective cohorts with validated anthropometric measurements for body mass index (BMI) and waist-hip ratio and other lifestyle factors. Diagnoses of CD and UC were confirmed through medical records or ascertained using validated definitions. We used Cox proportional hazards modeling to calculate pooled multivariable-adjusted HRs (aHRs) and 95% confidence intervals (CIs). RESULTS:Among 601,009 participants (age range, 18-98 years) with 10,110,018 person-years of follow-up, we confirmed 563 incident cases of CD and 1047 incident cases of UC. Obesity (baseline BMI ‡30 kg/m 2 ) was associated with an increased risk of CD (pooled aHR, 1.34; 95% CI, 1.05-1.71, I 2 [ 0%) compared with normal BMI (18.5 to <25 kg/m 2 ). Each 5 kg/ m 2 increment in baseline BMI was associated with a 16% increase in risk of CD (pooled aHR, 1.16; 95% CI, 1.05-1.22; I 2 [ 0%). Similarly, with each 5 kg/m 2 increment in early adulthood BMI (age, 18-20 years), there was a 22% increase in risk of CD (pooled aHR, 1.22; 95% CI, 1.05-1.40; I 2 [ 13.6%). An increase in waist-hip ratio was associated with an increased risk of CD that did not reach statistical significance (pooled aHR across quartiles, 1.08; 95% CI, 0.97-1.19; I 2 [ 0%). No associations were observed between measures of obesity and risk of UC.

ObjectiveTo estimate the proportion of cases of Crohn’s disease (CD) and ulcerative colitis (UC) that could be prevented by modifiable lifestyle factors.DesignIn a prospective cohort study of US adults from the Nurses’ Health Study (NHS; n=72 290), NHSII (n=93 909) and Health Professionals Follow-up Study (HPFS; n=41 871), we created modifiable risk scores (MRS; 0–6) for CD and UC based on established lifestyle risk factors, and healthy lifestyle scores (HLS; 0–9) derived from American healthy lifestyle recommendations. We calculated the population attributable risk by comparing the incidence of CD and UC between low-risk (CD-MRS≤1, UC-MRS≤2, HLS≥7) and high-risk groups. We externally validated our findings in three European cohorts: the Swedish Mammography Cohort (n=37 275), Cohort of Swedish Men (n=40 810) and European Prospective Investigation into Cancer and Nutrition (n=404 144).ResultsOver 5 117 021 person-years of follow-up (NHS, HPFS: 1986–2016; NHSII: 1991–2017), we documented 346 CD and 456 UC cases. Adherence to a low MRS could have prevented 42.9% (95% CI 12.2% to 66.1%) of CD and 44.4% (95% CI 9.0% to 69.8%) of UC cases. Similarly, adherence to a healthy lifestyle could have prevented 61.1% (95% CI 16.8% to 84.9%) of CD and 42.2% (95% CI 1.7% to 70.9%) of UC cases. In our validation cohorts, adherence to a low MRS and healthy lifestyle could have, respectively, prevented 43.9%–51.2% and 48.8%–60.4% of CD cases and 20.6%–27.8% and 46.8%–56.3% of UC cases.ConclusionsAcross six US and European cohorts, a substantial burden of inflammatory bowel diseases risk may be preventable through lifestyle modification.

Background and aims: There are limited data on alcohol dose and types and risk of Crohn's Disease (CD) and Ulcerative Colitis (UC). We therefore sought to comprehensively examine the association between alcohol consumption and risk of CD and UC. Methods:We conducted a prospective cohort study of 237,835 participants from the Nurses' Health Study, Nurses' Health Study II, and Health Professional Follow-Up Study. Alcohol consumption was obtained through questionnaires submitted every four years; additional covariates were obtained at two or four-year intervals. Cases were confirmed independently by two physicians through medical record review. We used Cox proportional hazards regression to estimate age and multivariable-adjusted hazards ratios and 95% confidence intervals.Results: Across 5,170,474 person-years of follow-up, 370 cases of CD and 486 cases of UC were documented. Increased consumption of alcohol intake was not associated with CD (Ptrend = 0.455) or UC (Ptrend = 0.745). Compared to non-users, the MV-adjusted HRs for 15.0 + g/day of alcohol intake group were 0.84 (95% CI 0.56, 1.24) for CD and 1.08 (95% CI 0.77, 1.51) for UC. In analyses of alcohol subtypes, we observed that only moderate consumption of beer (>1-4 servings/week) was marginally associated with reduced risk of CD, while consumption of >4 servings/week of liquor was associated with an increased risk of UC. Conclusion:This prospective study did not identify a relationship between overall alcohol consumption and risk of CD or UC. Our suggestive associations between alcohol types and risk of CD and UC deserve additional investigation.The Handling Editor for this article was Professor Peter Gibson, and it was accepted for publication after full peer-review.

Summary Background Although immune‐mediated diseases (IMDs) including inflammatory bowel diseases (IBDs) are known to cluster, to what extent this is due to common environmental influences is unknown. Aim To examine the incidence of IBD in individuals with another IMD. Methods We used data from the prospective Nurses' Health Study II cohort (1995‐2017) to examine the effect of diagnoses of several common IMDs on subsequent risk of Crohn's disease (CD) or ulcerative colitis (UC) using Cox proportional hazards models, adjusting for detailed diet and lifestyle confounders. Results We documented 132 cases of CD and 186 cases of UC over 2 016 163 person‐years of follow‐up (median age at IBD diagnosis 50 years). Compared to participants with no history of IMD, the HRs of CD for those with 1 and ≥ 2 IMDs were 2.57 (95% CI 1.77‐3.74) and 2.74 (95% CI 1.36 to 5.49), respectively (Ptrend < 0.0001). This association was only modestly attenuated by adjustment for environmental risk factors (HR 2.35 and 2.46, respectively). The risk of UC was not increased, with multivariable‐adjusted HRs of 1.22 (95% CI 0.85‐1.76) and 1.33 (95% CI 0.67‐2.65) for those with 1 and ≥ 2 IMDs, respectively, compared to those with none (Ptrend 0.16) (Pheterogeneity comparing CD and UC 0.037). Asthma, atopic dermatitis, psoriasis and rosacea were individually associated with higher risk of CD (HR ranging from 2.15 to 3.39) but not UC. Conclusions Individuals with one or more IMDs are at an increased risk for CD but not UC.

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Background To assess the relationship between diet quality and risk of older-onset Crohn’s disease (CD) and ulcerative colitis (UC). Methods We conducted a prospective cohort study of 83,147 participants from the Swedish Mammography Cohort and the Cohort of Swedish Men. We used food frequency questionnaire to calculate adherence scores to multiple derived health diet patterns: Alternate Healthy Eating Index (AHEI), Healthy Eating Index-2015 (HEI-2015), Healthful Plant-Based Diet Index (HPDI), and modified Mediterranean Diet Score (mMED) at baseline in 1997 in both cohorts. Diagnoses of CD and UC were retrieved from the Swedish Patient Register. We used Cox proportional hazards modeling to estimate the adjusted hazard ratios (HRs) and 95% CIs. Findings Through December of 2017, we confirmed 164 incident cases of CD and 395 incident cases of UC. Comparing the highest to the lowest quartiles, the adjusted HRs of CD were 0.73 (95% CI, 0.48, 1.12, Ptrend = 0.123) for AHEI; 0.90 (0.57, 1.41, Ptrend = 0.736) for HEI 2015; 0.52 (95% CI 0.32, 0.85, Ptrend = 0.011) for HPDI; and 0.58 (95% CI 0.32, 1.06, Ptrend = 0.044) for mMED. In contrast, we did not observe an association between any diet quality score and risk of UC. Interpretation We found that several healthy eating patterns were associated with a lower risk of older-onset CD. Our findings provide a rationale for adapting different healthy dietary patterns based on individuals’ food preferences and traditions for designing future prevention strategies for IBD.