Colon Capsule Endoscopy-Measured Colonic Transit Time Is Associated with Frailty in Older Adults

Background and Objectives: Although the association between frailty and constipation in older adults has attracted growing attention, evidence linking the Clinical Frailty Scale (CFS) to colonic transit time (CTT) remains scarce. In this retrospective study, we examined this association using colon capsule endoscopy (CCE). Materials and Methods: We enrolled 124 older adults (64 men, 60 women) aged ≥ 65 years (mean age 74.6 ± 5.6) who underwent CCE for colorectal polyp screening at Aishinkai Nakae Hospital, Japan, between January 2014 and July 2024. CTT was determined at the time of CCE, and frailty was assessed with the Japanese version of the CFS. To avoid the oversimplification inherent in a strict dichotomy, participants were analyzed primarily as three ordered categories-Robust (CFS 1-2; n = 73), Intermediate (CFS 3-4; n = 43), and Frail (CFS 5-7; n = 8)-and, for comparability with previous reports, also as a Robust versus Non-robust (CFS 3-7; n = 51) dichotomy. The independent association between CFS and CTT was examined with three complementary multivariable linear regression models (Model 2: CFS continuous; Model 3: CFS three-category ordinal; Model 3b: CFS three-category dummy with Robust as reference), each adjusted for 10 covariates: age, sex, body mass index, type 2 diabetes mellitus, laxative use, anticholinergic drug use, psychotropic drug use, hypothyroidism, smoking history, and history of abdominal surgery. Results: CTT rose stepwise across the three frailty categories (Robust: 132.0 min [IQR 81.0-229.0], 157.9 ± 99.9; Intermediate: 198.0 min [90.5-267.0], 186.1 ± 99.8; Frail: 241.5 min [199.0-320.5], 295.8 ± 181.3; Kruskal-Wallis p = 0.027; Jonckheere-Terpstra P for trend = 0.017); the dichotomous comparison was concordant (median 214.0 vs. 132.0 min; Mann-Whitney U U = 1441.5; p = 0.033). A graded dose-response-like relationship was further supported by Spearman correlation between the CFS score and CTT (ρ = 0.232; p = 0.009). Women had significantly longer CTT than men (median 189 vs. 121 min; p = 0.013), and the three-group trend was significant within the female subgroup (Kruskal-Wallis p = 0.032) but not within men (p = 0.138). In multivariable analysis, CFS remained independently associated with CTT prolongation both as a continuous score (Model 2: β = 36.6 per 1-point increase; 95% CI 17.3 to 56.0; p < 0.001) and as an ordinal three-category predictor (Model 3: β = 52.7 per one-step advance; 95% CI 19.7 to 85.8; p = 0.002). In the dummy-coded specification (Model 3b), the Frail-versus-Robust contrast was markedly significant (β = 155.4 min; 95% CI 71.5 to 239.3; p < 0.001), whereas the Intermediate-versus-Robust contrast was not (β = 27.0; 95% CI -15.5 to 69.5; p = 0.210). Female sex retained independent significance across models (β ≈ 47-49 min; p = 0.016-0.021). The original dichotomous Non-robust versus Robust specification (Model 1) was no longer significant after full adjustment (p = 0.372). Conclusions: Frailty progression, as assessed by the CFS, is independently and monotonically associated with prolonged CTT in older adults, with the effect becoming statistically manifest predominantly at the more advanced end of the frailty spectrum and particularly in women. Although these findings do not establish causality between frailty and constipation-and frailty itself reflects a multifactorial age-related process that may not be fully reversible-CCE-measured CTT provides an objective, radiation-free physiological biomarker of frailty-related bowel dysfunction that may support risk stratification and inform future interventional trials targeting potentially modifiable components of the gut-muscle axis.