Listener effort measures clinically meaningful change of dysarthria in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative motor neuron disease that can cause progressive bulbar dysfunction and dysarthria, resulting in reduced quality of life. Quantitative motor speech analysis can identify features of dysarthria that worsen with ALS progression but are not, inherently, clinically meaningful. Listener effort (LE) is a clinician-rated feature describing how much effort the listener needs to exert to understand the dysarthric speaker. This study investigated whether LE could act as a clinically meaningful measure of ALS dysarthria that could be used as an outcome measure in clinical trials. The Everything ALS Speech Study obtained longitudinal clinical information and speech recordings from 292 participants. In a subset of 125 participants, we measured speaking rate and three speech-language pathologists (SLPs) with expertise in ALS rated LE. We also built and tested a LE prediction algorithm to predict the SLPs' rating of LE. In addition, all speech recordings and associated clinical data are now being made available to ALS researchers via the Everything ALS portal. LE intra- and inter-rater reliability was very high (ICC 0.94-0.95). LE correlated with other measures of dysarthria at baseline and changed over time in participants with ALS (slope 0.77 pts/month, SE = 0.15, P < 0.001) but not controls (slope 0.005 pts/month, SE = 0.02, P = 0.807). The slope of LE progression was faster in people with bulbar onset than non-bulbar onset ALS (1.66 points/month versus 0.42 pts/month; P < 0.001) but was similar in all participants who had bulbar dysfunction at baseline, regardless of ALS site of onset (1.52 pts/month for bulbar onset versus 0.98 pts/month for non-bulbar onset with current bulbar involvement; P = 0.36). The LE prediction model predicted the true LE, with an average R² of 0.83 ± 0.07. Dysarthria is associated with decreased quality of life in people with ALS. Quantitative measures of dysarthria in ALS could be useful as ALS clinical trial outcome measures, providing insight into the progression of bulbar symptoms. Speaking rate quantifies progression but is variable across speaking stimuli, emotional states and contextual factors. LE is more inherently clinically meaningful, can be measured reliably by SLPs, changes quantitatively over time and is highly reproducible, thus may be useful as a clinical outcome assessment for ALS clinical trials. Furthermore, a LE prediction model is effective at predicting LE scores and should be validated on an external dataset.