Introduction: Fatigue often impacts daily activities in patients with IBD and is commonly reported even in patients with inactive disease. We explored the impact of fatigue on work productivity and activity impairment (WPAI) and health care utilization (HCU). Methods: Data were analyzed from the CorEvitas IBD Registry, a prospective cohort of adult patients with Crohn’s Disease (CD) or ulcerative colitis (UC). Using data collected between May 3, 2017 and April 1, 2022, we compared WPAI and HCU among 1) subjects with high fatigue (PROMIS score > 55) vs low fatigue (PROMIS score < 55) at enrollment and 2) subjects whose fatigue score worsened vs subjects with persistently high fatigue at 6 months. Disease activity was assessed with Harvey Bradshaw Index (CD) or Partial Mayo (UC). Descriptive statistics, adjusted odds ratios and 95% CIs are reported. Results: High fatigue at enrollment was reported in 47% of 640 CD and 38% of 569 UC patients with 56% and 39% in remission, respectively. For both CD and UC, patients with high fatigue reported more absenteeism, presenteeism, work productivity loss, and daily activity impairment, and higher rates of HCU at enrollment compared to those with low fatigue (Table). In adjusted analyses, 17% of CD subjects had worsened fatigue at 6 months which correlated with 2.7 increased odds of worsening presenteeism (95% CI: 1.19-6.26) and a 2.6 increased odds of worsening daily activity impairment (95% CI 1.45-4.72) compared to those with persistently high fatigue (Figure a). For UC, high fatigue correlated with 2.9 increased odds of an IBD-related hospitalization (95% CI 1.02-7.99) and 3.8 increased odds of having an ER visit (95% CI 1.28-11.01) in the following 6 months. Further, 13% of UC subjects had worsened fatigue at 6 months and were found to have 2.2 increased odds of worsening daily activity impairment (95% CI 1.06-4.59) compared to those with persistently high fatigue (Figure b). Conclusion: Our data show that fatigue is prevalent in both CD and UC and persists in the absence of active inflammation. More severe fatigue is associated with concurrent work productivity and activity impairment in both UC and CD patients and more IBD-related HCU in the UC subjects. Treatment approaches that improve fatigue in our IBD population may help to lessen further disability.Figure 1.: Adjusted Association Between Worsening Fatigue vs Persistently High Fatigue at 6 Months and Change in Employment, Work Productivity and Activity Impairment, and Health Care Utilization at 6 Months in Patients with Crohn’s Disease or Ulcerative Colitis * Adjusted odds ratios were obtained using logistic regression models adjusted for age, sex, education, marital status, current alcohol use, history of CVD, history of respiratory, history of depression, history of anxiety, number of prior biologics/JAKi/S1P, concomitant steroids, duration of current IBD therapy, Harvey Bradshaw index score (continuous), and WPAI current employment † Adjusted odds ratios and p values were obtained using logistic regression models adjusted for age, sex, BMI continuous, private insurance, marital status, history of respiratory, history of anxiety, history of other non-serious medical condition, time since IBD diagnosis, prior IST experienced, prior steroid experienced, Harvey Bradshaw Index score (continuous), and WPAI current employment ‡ Adjusted odds ratios were obtained using logistic regression models adjusted for age, sex, smoking status, current alcohol use, history of CVD, history of depression, history of anxiety, history of other non-serious medical condition, pan-colitis, concomitant biologics/JAKi/S1P, concomitant 5-ASAs, duration of current IBD therapy (years), and Partial Mayo score (continuous) ‖ Adjusted odds ratios were obtained using logistic regression models adjusted for white race, Hispanic ethnicity, BMI categorical, smoking status, history of anxiety, history of other non-serious medical conditions, proctitis, pan-colitis, prior-antibiotic experienced, concomitant biologics/JAKi/S1P, concomitant 5-ASAs, and Partial Mayo score (continuous). Table 1. - Baseline Work Projectivity and Activity Impairment and Health Care Utilization Among Patients with Crohn’s Disease or Ulcerative Colitis having High Fatigue (PROMIS score ≥ 55) versus Low Fatigue (PROMIS score < 55) at Enrollment High Fatigue Low Fatigue Unadjusted p value Crohn's disease n=299 n=341 Absenteeism 45/169 (27%) 28/209 (13%) 0.001 Presenteeism 147/174 (85%) 113/222 (51%) < 0.001 Work productivity loss 143/167 (86%) 112/208 (54%) < 0.001 Daily activity impairment 255/298 (86%) 193/339 (57%) < 0.001 IBD-related hospitalizations 206/299 (69%) 203/340 (60%) 0.016 IBD-related ER visits 193/299 (65%) 185/340 (54%) 0.009 Ulcerative Colitis n=218 n=351 Absenteeism 48/131 (37%) 23/215 (11%) < 0001 Presenteeism 102/139 (73%) 120/232 (52%) < 0001 Work productivity loss 99/130 (76%) 117/215 (54%) < 0001 Daily activity impairment 176/217 (81%) 199/351 (57%) < 0001 IBD-related hospitalizations 109/218 (50%) 144/351 (41%) 0.036 IBD-related ER visits 111/218 (51%) 132/350 (38%) 0.002