LAUSR

Importance The incidence of inflammatory bowel disease (IBD) is increasing in newly industrialized countries but disease etiologies remain unclear. Objective To investigate the association between physical fitness and subsequent IBD risk among children and adolescents in Taiwan. Design, Setting, and Participants This nationwide cohort study was conducted between January 1, 2010, and December 31, 2018. Data sources included the Taiwan National Health Insurance Research Database, the National Student Fitness Tests Database, and the Air Quality Monitoring System Database. This study included students who were aged 10 years, completed physical fitness tests between grades 4 and 13, and had at least 1 year of follow-up. Data analysis was last performed on January 15, 2023. Exposures Physical fitness tests included cardiorespiratory endurance (CE; number of minutes to complete an 800-m run), musculoskeletal endurance (ME; number of bent-leg curl-ups in 1 minute), musculoskeletal power (MP; standing broad jump distance), and flexibility fitness (FF; 2-leg sit-and-reach distance). Main Outcomes and Measures Subsequent risk of IBD was compared among students based on physical fitness test results. Six-year cumulative incidences and hazard ratios (HRs) were calculated after adjusting for competing mortality. Performance was reported in quantiles, ranging from 1 (best) to 4 (poorest). Results There were 4 552 866 students who completed physical fitness tests between grades 4 and 13; among these students, 1 393 641 were aged 10 years and were included in the analysis. Six-year cumulative incidence of IBD risk was lowest among students in the best-performing quantile of CE (quantile 1, 0.74% [95% CI, 0.63%-0.86%]; P < .001), ME (0.77% [0.65%-0.90%]; P < .001), and MP (0.81% [0.68%-0.93%]; P = .005) compared with students in quantiles 2 through 4, respectively; however, no association was observed for quantiles of FF. After adjusting for competing HRs for mortality and other confounders, better CE was inversely associated with IBD risk (adjusted HR, 0.36 [95% CI, 0.17-0.75]; P = .007). Other measures of physical fitness were not independently associated with IBD risk. Conclusions and Relevance The results of this study suggest that CE was inversely associated with IBD risk among children and adolescents, but ME, MP, and FF were not independently associated with IBD risk. Future studies that explore the mechanisms are needed.