Use of the 10-meter timed walk for monitoring long-term gait progression in human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis: a 10-year analysis from the Japanese HAM-net registry

Abstract Background Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic neuroinflammatory disease that affects approximately 0.3% of individuals with HTLV-1 infection in Japan. Considering the rarity of HAM/TSP, data on the natural progression of walking disability and its correlation with outcome measures, such as the Osame’s Motor Disability Score (OMDS), remain limited. This observational study analyzed longitudinal data from the Japanese HAM patient registry “HAM-net” to identify appropriate clinical outcome measures for evaluating treatment efficacy in HAM/TSP. Methods We incorporated 10-meter timed walk (10mTW) data from patients registered in the HAM-net. The natural course of 10mTW performance was assessed, and its correlation with various outcome measures was analyzed to evaluate the use of the 10mTW as a primary outcome measure in HAM/TSP clinical trials. Results This study included 142 patients with at least two 10mTW data; 77.5% were female, with a mean age at onset and HAM diagnosis of 45.7 and 53.8 years, respectively. The geometric mean (95% confidence interval CI) for the 10mTW at baseline, Year 5, and Year 10 was 12.6 s (95% CI, 11.5 s–13.8 s), 14.3 s (95% CI, 12.7 s–16.1 s), and 16.3 s (95% CI, 13.6 s–19.5 s), respectively. The 10mTW at Years 5 and 10 increased by 7.37% (95% CI, −0.39%–15.73%) and 42.10% (95% CI, 19.92%–68.39%), respectively. The 10mTW exhibited significant positive correlations with motor disability scores, such as the OMDS and Instituto de Pesquisa Clinica Evandro Chagas-1 (IPEC-1), and activities of daily living (ADL) scales, such as the Health Assessment Questionnaire (HAQ). Conclusions This study revealed a 42.10% increase in the 10mTW over 9 years, with significant correlations to motor disability scores (OMDS and IPEC-1) and ADL scales (HAQ). These findings support the use of 10mTW performance as a primary outcome measure in HAM/TSP clinical trials, emphasizing its value for long-term assessment of gait progression.