Shorter Sentence Length Maximizes Intelligibility and Speech Motor Performance in Persons With Dysarthria Due to Amyotrophic Lateral Sclerosis

Purpose: The purpose of this study was to investigate the effect of sentence length on intelligibility and measures of speech motor performance in persons with amyotrophic lateral sclerosis (ALS) and to determine how these effects were influenced by dysarthria severity levels. Method: One hundred thirty-one persons with ALS were included in this study, stratified into 4 dysarthria severity groups. All participants produced sentences from 5 to 15 words in length. Intelligibility, speaking rate, and measures of speech pausing behavior (i.e., total speech duration, total pause duration, and mean speech event duration) were measured for each sentence. Linear mixed-effects models were used to determine the effect of sentence length on speech measures for speakers at different dysarthria severity levels. Results: Results showed that speech intelligibility significantly declined at longer sentence lengths only for the speakers with ALS who had more advanced dysarthria symptoms; however, speakers with mild-to-severe dysarthria showed significant declines in speaking rate and speech pausing behavior at longer sentence lengths. Conclusions: Findings suggest that producing shorter sentences may help maximize intelligibility for speakers with moderate-to-severe dysarthria secondary to ALS and may be a beneficial compensatory strategy for preserving motor effort for all speakers with dysarthria secondary to ALS.