Physical activity, sedentary behavior and risk of inflammatory bowel disease: a prospective cohort study in the UK Biobank.

BACKGROUND: Evidence suggests that physical activity (PA) may mitigate chronic inflammation, while sedentary behavior (SB) could exacerbate gut dysbiosis-key mechanisms in inflammatory bowel disease (IBD). However, epidemiological data on their independent and joint associations with IBD risk remains inconsistent and inconclusive. OBJECTIVE: This cohort study aimed to examine the separate and joint association of PA and SB with IBD risk. METHODS: The research contained 355,021 people with no IBD at baseline in the UK Biobank. PA was measured using the International PA Questionnaire(IPAQ), calculating metabolic equivalent tasks (METs) min/wk based on the frequency and duration of walking, moderate, and vigorous activities. SB was assessed by self-reported total time spent driving, using computers, and watching television in a day. Using Cox proportional hazard models to evaluate the hazard ratios (HRs) and 95% confidence intervals (CIs) for IBD, Crohn's disease (CD) and ulcerative colitis (UC) risks, while restricted cubic splines (RCS) assessing nonlinear relationships. RESULTS: During 13.6 years of follow-up, 2,242 incident IBD cases (664 CD and 1,481 UC) were recorded. Compared to the low level of PA, IBD risk was found to be lower for moderate and high PA, with HRs of 0.80 (95% CI: 0.72-0.89, p < 0.001) and 0.87 (95% CI: 0.78-0.98, p = 0.02), respectively. We also found a nonlinear correlation of PA with IBD risk (p < 0.05 for nonlinearity), with a moderate level of PA (~ 2000 MET min/wk) offering the lowest risk. Besides, each additional hour of SB per day increased IBD risk (HR: 1.03; 95% CI: 1.01-1.05; p < 0.001). The risk reduction from moderate and high levels of PA attenuated the adverse effects of long SB (≥ 6 h/day), decreasing the risk by 18% and 27%, respectively. The results of PA and SB together on IBD risk showed that participants with low PA and long SB have the highest IBD risk. CONCLUSIONS: The results revealed that promoting PA and reducing SB synergistically lower IBD risk. Individuals combining high PA with lowest SB time are at the lowest probability of developing IBD.