A retrospective investigation of the relationship between baseline covariates and rate of ALSFRS-R decline in ALS clinical trials

The revised ALS functional rating scale (ALSFRS-R) is a longitudinal measure of global function commonly used to assess progression of amyotrophic lateral sclerosis (ALS), and as an endpoint in ALS clinical trials. Understanding how baseline covariates affect the rate of functional decline in ALS offers valuable information to clinical trialists. We used a mixed modeling approach in a retrospective study of the pooled resource open-Access ALS clinical trials database to elucidate the associations between baseline covariates and the rate of ALSFRS-R decline over time. In a cohort of 3203 patients followed for an average of 337 days, older age at disease onset (p < 0.001), less time since disease onset (p < 0.001), and bulbar site of onset (p < 0.001) were associated with a significantly faster decline of the ALSFRS-R, while sex did not have a statistically significant effect (p = 0.82). Selective inclusion of ‘age at disease onset’ and ‘time since disease onset’ as covariates provided the best tradeoff between model fit and model precision. The effect of bulbar onset on rate of disease progression was primarily due to accelerated decline in the bulbar subscale of the ALSFRS-R. These findings, which are novel in the clinical trial time frame, contribute to the understanding of disease trajectory in ALS and can be used to guide future design and analysis of clinical trials.