Purpose: This study aimed to investigate whether rhythm metrics are sensitive to change in speakers with mild hypokinetic dysarthria, whether such changes can be detected in reading and spontaneous speech, and whether diadochokinetic (DDK) performance relates to rhythmic properties of speech tasks. Method: Ten people with Parkinson’s Disease (PwPD) with mild hypokinetic dysarthria and ten healthy control speakers produced DDK repetitions, a reading passage and a spontaneous monologue. Articulation rate, as well as ten rhythm metrics were applied to the speech data. DDK performance was captured by mean, standard deviation (SD) and coefficient of variation (CoV) of syllable duration. Results: Group differences were apparent across both speech tasks, but mainly in spontaneous speech. The control speakers changed their rhythm performance between the two tasks, whereas the PwPD displayed a more constant behaviour. The correlation analysis of speech and DDK tasks resulted in few meaningful relationships. Conclusions: Rhythm metrics appeared to be sensitive to mild levels of impairment in PwPD. They are thus suitable for use as diagnostic or outcome measures. In addition, we demonstrated that conversational data can be used in the investigation of rhythm. Finally, the value of DDK tasks in predicting the rhythm performance during speech could not be demonstrated successfully
