Accelerated Muscle Strength Decline and Reduced Lean Mass in Adults with Treated Inflammatory Bowel Disease: A NHANES Study

Background: Muscle loss is associated with chronic systemic inflammation and metabolic stress in the context of inflammatory bowel disease (IBD). However, studies that assessed the population-level effects of treated IBD on muscle health are limited. Methods: In this study, pooled National Health and Nutrition Examination Survey 2011-2014 data of adults aged 20-59 years were analyzed through dual-energy X-ray absorptiometry and grip strength measurements. The treated IBD status was determined using prescription medication records, prioritizing specificity to capture individuals with clinically treated diseases rather than all IBD cases. Survey-weighted regression models were used to assess the associations with grip strength, appendicular lean mass index (ALMI), and muscle quality, including an IBD × age interaction. Results: Among 5,522 adults, 25 were treated with IBD, requiring careful interpretation due to the limited effective sample size. IBD was associated with significantly lower grip strength and reduced ALMI after adjusting for age, sex, and body mass index. A significant interaction indicated a steeper age-related decline in grip strength among adults with IBD. No significant differences in muscle quality were observed between the groups. Conclusion: Muscle loss in patients with treated IBD was related to reduced lean body mass and a pattern consistent with faster age-related neuromuscular loss. These findings highlight an opportunity for the early identification of functional vulnerability using continuous muscle phenotypes and emphasize the potential role of modifiable lifestyle interventions, including physical activity, resistance training, and nutritional optimization, in preserving muscle health and improving long-term functional decline in adults with IBD.