Early achieved ambulation is associated with reduced venous thromboembolism among hospitalised medicine patients

Background Hospital-acquired venous thromboembolism (VTE) remains a major source of preventable morbidity and mortality. Although immobility is a recognised risk factor, inpatient mobility is rarely quantified using standardised measures, and the independent association between achieved ambulation and VTE remains unclear. Methods We conducted a retrospective cohort study of adult medicine inpatients at two academic hospitals (January 2021–April 2024). Analyses were restricted to patients with ambulatory capability based on admission Activity Measure for Post-Acute Care (AM-PAC) mobility scores (16–24). Early achieved ambulation was defined as a mean Johns Hopkins Highest Level of Mobility (JH-HLM) score ≥6 (≥10 steps) during hospital days 1–3. Propensity scores incorporated demographics, comorbidity burden, baseline mobility, Padua VTE risk factors (excluding mobility) and early clinical severity indicators. Stabilised inverse propensity score weighted Poisson regression models estimated rate ratios (RRs) for hospital-acquired VTE confirmed by imaging and chart review. Prespecified exploratory analyses were stratified by admission chemoprophylaxis status. Results Among 16 458 eligible admissions, 47% achieved early ambulation. VTE occurred in 0.3% versus 0.7% of early ambulatory versus non-ambulatory patients, respectively. Early achieved ambulation was associated with a 47% lower VTE rate (RR 0.53, 95% CI 0.34 to 0.84). In exploratory analyses stratified by chemoprophylaxis status, the association was statistically significant among patients not prescribed chemoprophylaxis (RR 0.40, 95% CI 0.21 to 0.79) but not among those prescribed chemoprophylaxis (RR 0.63, 95% CI 0.35 to 1.16). Conclusions Early achieved ambulation was associated with lower hospital-acquired VTE rates among patients with ambulatory capability. These findings support mobility as a measurable, potentially modifiable component of multimodal VTE prevention that may complement pharmacological prophylaxis.