Modeling the relationship between function, cognition, and motor ability in Huntington's Disease

Background
In Huntington’s Disease, motor and cognitive impairment both contribute to functional impairment, where a person’s ability to work and care for themselves becomes limited.
Objectives
The author sought to predict a subject’s functional impairment given the subject’s measured cognition and motor impairment.
Methods
Ordinal models were developed and fit to baseline data from the global observational study ENROLL-HD (N = 9,072). The Symbol Digits Modality Test (SDMT) was used to quantify cognition and, the Total Motor Score (TMS) was used to quantify motor ability. The models predicted the Total Functional Capacity (TFC) and Independence Score (IS) from the SDMT and TMS.
Results
Both SDMT and TMS were statistically significant predictors of function. The predicted function showed strong correlation with the observations (Pearson r of 0.82 for TFC and 0.84 for IS). The models were applied to predict functional improvements resulting from hypothetical treatments that improved SDMT or TMS. For example, it was projected that a 5 point improvement in SDMT would cause a mean improvement of 0.33 in TFC.
Conclusions
The models have implications for drug development, where rapidly acting symptomatic treatments may show improved cognitive or motor performance, but functional effects may be delayed or require large sample sizes to detect. Predicting functional effects with these models may support sample size calculations for future trials.

研究背景
在亨廷顿病（Huntington’s Disease）中，运动障碍与认知障碍均可导致功能障碍，使患者的工作能力及自我照护能力受限。
研究目标
本研究旨在基于受试者已测得的认知与运动障碍情况，预测其功能障碍程度。
研究方法
本研究构建了有序模型（Ordinal models），并将其拟合至全球观察性研究ENROLL-HD的基线数据（N=9,072）。研究采用符号数字模态测试（Symbol Digits Modality Test, SDMT）量化认知水平，以运动总评分（Total Motor Score, TMS）评估运动能力；模型基于SDMT与TMS预测总功能能力（Total Functional Capacity, TFC）与独立评分（Independence Score, IS）。
研究结果
SDMT与TMS均为功能状态的统计学显著预测因子。预测所得功能状态与实际观测值具有较强相关性（TFC的皮尔逊相关系数r为0.82，IS为0.84）。本研究将模型用于预测可改善SDMT或TMS的假想治疗方案所带来的功能改善情况。例如，经预测，SDMT提升5分可使TFC平均提升0.33分。
研究结论
本研究构建的模型对药物研发具有指导意义：快速起效的对症治疗或许可改善认知或运动表现，但功能改善效应可能延迟显现，或需要大样本量才能被检测到。利用这些模型预测功能效应，可为未来临床试验的样本量计算提供支持。